Screening tests
Testing for M. tuberculosis may begin with a TB screening test. This is not used as a general screen but is targeted at those who are at a high risk for contracting the disease and at those who work or live with high-risk people. The TB screening test may also be done as part of a physical examination prior to starting school or a new job.
The TB skin test is performed on the patient's skin by injecting a purified protein derivative (PPD) solution just under the skin. This provokes a hypersensitivity skin reaction (a red raised bump) in those who may have been infected by M. tuberculosis. The reaction is evaluated by a health care worker at 48 or 72 hours. Positive results may indicate a latent TB infection and should be followed by other tests, such as chest X-rays, to look for signs of active disease. False-positive results may be seen in people who have had a BCG (Bacille Calmette-Guérin) vaccination while false-negative results may be seen in those with weakened immune systems. This method of screening also requires a second visit for the results to be evaluated.
The interferon gamma release assays (IGRAs) are relatively new blood tests that can be used as an alternative or follow up to the TB skin test to help diagnose a latent TB infection. It is not affected by previous IGRA, TB skin tests, or by BCG vaccination. It does not require the patient to return in 48 to 72 hours for evaluation, and there is no local skin reaction. However, these tests have special handling and transport time restrictions. There are limited data on its use with children and those with suppressed immune systems. A positive IGRA must be followed up in a similar fashion to a positive TB skin test in order to determine if an active infection is present.
Active Tuberculosis
AFB Smear and Culture
To diagnose TB of the respiratory tract, 3 to 5 sputum specimens are collected first thing in the morning on different days when they are most likely to contain the most mycobacteria. If extrapulmonary TB is suspected, samples are collected based upon where in the body the infection is likely to be. Multiple samples of gastric (stomach) washings/aspirates or urine may be collected and submitted to the laboratory. Sometimes cerebrospinal fluid (CSF), biopsied tissue, or other body fluids are also collected.
A presumptive diagnosis of TB can be made by examining a smear of the patient's specimen under the microscope after it has been treated with a special stain to detect acid fast bacteria (AFB). Positive AFB smears are likely to indicate a TB infection since M. tuberculosis is the most common acid-fast bacillus in the lungs, but the smears cannot distinguish between the different species of "acid-fast" bacilli. A culture is required for a definitive diagnosis.
AFB cultures are performed on respiratory samples or other body fluid samples. Specialized nutrient media and prolonged incubation provide a supportive environment for the slow-growing mycobacteria. The results of cultures are definitive, but they take time - days to several weeks for positive samples. Cultures are held for six to eight weeks before being reported as negative. Once M. tuberculosis has been identified and treatment has begun, AFB smears and cultures are used to monitor the effectiveness of treatment.
TB molecular tests (nucleic acid amplification test, NAAT) detect the genetic material of M. tuberculosis. They are useful because they can generally provide results in about 24 hours as opposed to the several weeks required for culture. The 2009 guidelines from the Center for Disease Control and Prevention (CDC) recommend that a TB NAAT be performed on at least one sample from someone with signs and symptoms of TB. The results are evaluated in conjunction with results of an AFB smear. Like AFB smears, both positive and negative results must be confirmed with AFB cultures. However, if both AFB smear and molecular test are positive, the doctor will begin treatment of the affected person before results of the culture are available.
Susceptibility testing is done to determine if the strain causing the infection has developed resistance to the drugs used most often to treat the infection. Testing can be performed on media containing the antibiotic used to treat TB, which can take several weeks for the result, or testing can be done in a broth culture and results can be available in 7 days. There are molecular tests available that can also be used to detect specific genes in the DNA of the bacteria that confer resistance to certain drugs. However, these tests are currently only available in areas outside of the United States.
A liquid culture method called Microscopic-Observation Drug-Susceptibility (MODS) assay has been developed. This method takes only about 7 days to diagnose TB and detects bacterial resistance to antibiotics. It can recognize the presence of mycobacteria much more quickly than traditional culture and can help health care providers diagnose and treat the disease at an earlier stage. It has the potential to help control the spread of infectious TB in resource-limited countries. The benefits and limitations of this test are being evaluated.
A rapid, automated molecular test that detects the genetic material of TB has been developed to help diagnose infections. Within two hours, the test can detect the presence of TB and determine if it is resistant to one of the most commonly prescribed drugs used to treat the infection, rifampin. In 2010, the World Health Organization endorsed use of the test, but it is not currently sold in the US as it has not yet been approved by the US Food and Drug Administration (FDA).
Non-Laboratory Tests
X-rays are often used as a follow-up to positive TB skin tests to look for signs of mycobacteria growth and to help determine whether someone has active tuberculosis or a latent TB infection. Infection with TB can cause a number of characteristic findings on x-rays, including cavities (holes) and calcification in organs such as the lungs and kidneys. More information on radiological tests can be found at RadiologyInfo.
http://labtestsonline.org/understanding/conditions/tuberculosis/?start=3
Showing posts with label latent tuberculosis. Show all posts
Showing posts with label latent tuberculosis. Show all posts
Monday, 18 July 2011
Sunday, 12 June 2011
TUBERCULOSIS: Australia: Refugees in Darwin infected with tuberculosis
Myles Morgan : Jun 6, 2011
The Northern Territory Centre for Disease Control says tests have shown almost a third of recently arrived refugees in Darwin have latent tuberculosis.
In three years of testing to 2009, the centre found 146 people had the infection.
It means they had been exposed to tuberculosis and could become infectious later in life.
Dr James Trauer from the Centre for Disease Control says it is important those who could become infectious are identified.
"Probably the most important part of managing TB on a public health level, and protecting the public from TB, is identifying people who are infectious and treating them appropriately," he said.
"The second most important thing to do after that is to screen people who might become infectious later."
Tuberculosis (TB) is a highly contagious disease that spreads through the air like a common cold.
According to the World Health Organisation (WHO), people infected with TB bacilli will not necessarily become sick.
The WHO says one-third of the world's population is currently infected with the TB bacillus.
http://www.abc.net.au/news/stories/2011/06/06/3236636.htm
The Northern Territory Centre for Disease Control says tests have shown almost a third of recently arrived refugees in Darwin have latent tuberculosis.
In three years of testing to 2009, the centre found 146 people had the infection.
It means they had been exposed to tuberculosis and could become infectious later in life.
Dr James Trauer from the Centre for Disease Control says it is important those who could become infectious are identified.
"Probably the most important part of managing TB on a public health level, and protecting the public from TB, is identifying people who are infectious and treating them appropriately," he said.
"The second most important thing to do after that is to screen people who might become infectious later."
Tuberculosis (TB) is a highly contagious disease that spreads through the air like a common cold.
According to the World Health Organisation (WHO), people infected with TB bacilli will not necessarily become sick.
The WHO says one-third of the world's population is currently infected with the TB bacillus.
http://www.abc.net.au/news/stories/2011/06/06/3236636.htm
Monday, 6 June 2011
TUBERCULOSIS: UK immigrant screening: latent tuberculosis:
30 May 2011
The Lancet Infectious Disease: Jun 2011 Volume 11 Number 6 Pages 417 – 488
http://www.thelancet.com/journals/laninf/issue/current
Manish Pareek, John P Watson, L Peter Ormerod, Onn Min Kon, Gerrit Woltmann, Peter J White, Ibrahim Abubakar, Ajit Lalvani
Screening of immigrants in the UK for imported latent tuberculosis: a multicentre cohort study and cost-effectiveness analysis
Summary
Background
Continuing rises in tuberculosis notifications in the UK are attributable to cases in foreign-born immigrants. National guidance for immigrant screening is hampered by a lack of data about the prevalence of, and risk factors for, latent tuberculosis infection in immigrants. We aimed to determine the prevalence of latent infection in immigrants to the UK to define which groups should be screened and to quantify cost-effectiveness.
Methods
In our multicentre cohort study and cost-effectiveness analysis we analysed demographic and test results from three centres in the UK (from 2008 to 2010) that used interferon-γ release-assay (IGRA) to screen immigrants aged 35 years or younger for latent tuberculosis infection. We assessed factors associated with latent infection by use of logistic regression and calculated the yields and cost-effectiveness of screening at different levels of tuberculosis incidence in immigrants’ countries of origin with a decision analysis model.
Findings
Results for IGRA-based screening were positive in 245 of 1229 immigrants (20%), negative in 982 (80%), and indeterminate in two (0·2%). Positive results were independently associated with increases in tuberculosis incidence in immigrants’ countries of origin (p=0·0006), male sex (p=0·046), and age (p<0·0001). National policy thus far would fail to detect 71% of individuals with latent infection. The two most cost-effective strategies were to screen individuals from countries with a tuberculosis incidence of more than 250 cases per 100 000 (incremental cost-effectiveness ratio [ICER] was £17 956 [£1=US$1·60] per prevented case of tuberculosis) and at more than 150 cases per 100 000 (including immigrants from the Indian subcontinent), which identified 92% of infected immigrants and prevented an additional 29 cases at an ICER of £20 819 per additional case averted.
Interpretation
Screening for latent infection can be implemented cost-effectively at a level of incidence that identifies most immigrants with latent tuberculosis, thereby preventing substantial numbers of future cases of active tuberculosis.
Funding
Medical Research Council and Wellcome Trust.
http://centerforvaccineethicsandpolicy.wordpress.com/2011/05/30/uk-immigrant-screening-latent-tuberculosis/
The Lancet Infectious Disease: Jun 2011 Volume 11 Number 6 Pages 417 – 488
http://www.thelancet.com/journals/laninf/issue/current
Manish Pareek, John P Watson, L Peter Ormerod, Onn Min Kon, Gerrit Woltmann, Peter J White, Ibrahim Abubakar, Ajit Lalvani
Screening of immigrants in the UK for imported latent tuberculosis: a multicentre cohort study and cost-effectiveness analysis
Summary
Background
Continuing rises in tuberculosis notifications in the UK are attributable to cases in foreign-born immigrants. National guidance for immigrant screening is hampered by a lack of data about the prevalence of, and risk factors for, latent tuberculosis infection in immigrants. We aimed to determine the prevalence of latent infection in immigrants to the UK to define which groups should be screened and to quantify cost-effectiveness.
Methods
In our multicentre cohort study and cost-effectiveness analysis we analysed demographic and test results from three centres in the UK (from 2008 to 2010) that used interferon-γ release-assay (IGRA) to screen immigrants aged 35 years or younger for latent tuberculosis infection. We assessed factors associated with latent infection by use of logistic regression and calculated the yields and cost-effectiveness of screening at different levels of tuberculosis incidence in immigrants’ countries of origin with a decision analysis model.
Findings
Results for IGRA-based screening were positive in 245 of 1229 immigrants (20%), negative in 982 (80%), and indeterminate in two (0·2%). Positive results were independently associated with increases in tuberculosis incidence in immigrants’ countries of origin (p=0·0006), male sex (p=0·046), and age (p<0·0001). National policy thus far would fail to detect 71% of individuals with latent infection. The two most cost-effective strategies were to screen individuals from countries with a tuberculosis incidence of more than 250 cases per 100 000 (incremental cost-effectiveness ratio [ICER] was £17 956 [£1=US$1·60] per prevented case of tuberculosis) and at more than 150 cases per 100 000 (including immigrants from the Indian subcontinent), which identified 92% of infected immigrants and prevented an additional 29 cases at an ICER of £20 819 per additional case averted.
Interpretation
Screening for latent infection can be implemented cost-effectively at a level of incidence that identifies most immigrants with latent tuberculosis, thereby preventing substantial numbers of future cases of active tuberculosis.
Funding
Medical Research Council and Wellcome Trust.
http://centerforvaccineethicsandpolicy.wordpress.com/2011/05/30/uk-immigrant-screening-latent-tuberculosis/
TUBERCULOSIS: Australia: Refugees Can Be Effectively Treated To Prevent Tuberculosis
04 Jun 2011 : The Medical Journal of Australia
Almost one in three recently arrived refugees in Darwin tested positive for latent tuberculosis infection (LTBI), research published in the latest Medical Journal of Australia has found.
Researchers from the Centre for Disease Control, Northern Territory (CDC-NT) found that of 458 refugees screened between 1 February 2006 and 31 January 2009, 146 (31.9 per cent) were diagnosed with LTBI. LTBI implies past exposure to tuberculosis, leaving the individual susceptible to active infection later in life if not treated.
More than three in four of those diagnosed accepted treatment, and about half of those completed treatment.
All refugees aged 11 years and older who are being considered for entry into Australia are screened for active tuberculosis, and must be treated and cured before arriving in Australia.
Refugees are then screened on arrival in Darwin for latent tuberculosis.
LTBI was more prevalent among refugees from the Eastern Mediterranean region, yet those refugees had the lowest rate of treatment acceptance, CDC-NT Tuberculosis/Leprosy Unit registrar Dr James Trauer said.
"Our findings show that timely screening and treatment of LTBI in refugee groups is feasible," Dr Trauer said.
"Measures directed at maintaining contact with refugees after arrival, provision of culturally and linguistically appropriate support, better understanding of treatment barriers, and care for individuals with medication-related side effects are all likely to be effective strategies for improving treatment completion."
In a case study also published in the latest issue of the MJA, doctors from Dunedin Hospital reported that in 2010 an immigrant from Burma became the first person to be diagnosed in New Zealand with extensively drug-resistant tuberculosis (XDR-TB).
The 29-year-old man, who emigrated in 2006, had no personal history of TB. It took 66 days from the initial sample collection for a final laboratory report to confirm that the strain was XDR-TB, and the cost of the second-line drugs used to treat the man was NZ$10 000 per month, Dunedin Hospital Respiratory Consultant Dr Colin Wong said. "Although our experience indicates that there is potential for treatment success, definitive treatment guidelines are needed and more data are required to inform treatment and help contain spread," Dr Wong said.
"Confirming XDR-TB in a young man from Burma who had no history of previous TB treatment suggests that XDR-TB may be more common in Burma than has been widely believed, reinforcing the need for strengthening laboratory support networks and TB surveillance systems in South-East Asia."
In an accompanying editorial, infectious diseases expert Associate Professor Paul Johnson, Infectious Diseases Department, Austin Health said that while Australia was a low-risk country for XDR-TB, having recorded one case of XDR-TB in 2004 and one in 2010, a national response was needed.
That strategy must include sustaining and extending existing overseas programs that helped neighbouring countries control TB, while the next line of defence was the primary care clinician.
"Rapid diagnosis of pulmonary TB minimises secondary transmission, whatever the resistance pattern of the isolate," Professor Johnson said.
"Then we need to strengthen our local TB public health services and recognise that as TB resistance increases linearly, the cost and complexity of managing these cases increases exponentially.
"Finally, we need to keep up to date with new technology ... Molecular diagnostics are not yet perfect - we will need to retain culture-based methods for a while yet - but they are now becoming widely available and progressively cheaper.
"We need to be organised and up to date if we want to stay ahead of TB."
http://www.medicalnewstoday.com/releases/227427.php
Almost one in three recently arrived refugees in Darwin tested positive for latent tuberculosis infection (LTBI), research published in the latest Medical Journal of Australia has found.
Researchers from the Centre for Disease Control, Northern Territory (CDC-NT) found that of 458 refugees screened between 1 February 2006 and 31 January 2009, 146 (31.9 per cent) were diagnosed with LTBI. LTBI implies past exposure to tuberculosis, leaving the individual susceptible to active infection later in life if not treated.
More than three in four of those diagnosed accepted treatment, and about half of those completed treatment.
All refugees aged 11 years and older who are being considered for entry into Australia are screened for active tuberculosis, and must be treated and cured before arriving in Australia.
Refugees are then screened on arrival in Darwin for latent tuberculosis.
LTBI was more prevalent among refugees from the Eastern Mediterranean region, yet those refugees had the lowest rate of treatment acceptance, CDC-NT Tuberculosis/Leprosy Unit registrar Dr James Trauer said.
"Our findings show that timely screening and treatment of LTBI in refugee groups is feasible," Dr Trauer said.
"Measures directed at maintaining contact with refugees after arrival, provision of culturally and linguistically appropriate support, better understanding of treatment barriers, and care for individuals with medication-related side effects are all likely to be effective strategies for improving treatment completion."
In a case study also published in the latest issue of the MJA, doctors from Dunedin Hospital reported that in 2010 an immigrant from Burma became the first person to be diagnosed in New Zealand with extensively drug-resistant tuberculosis (XDR-TB).
The 29-year-old man, who emigrated in 2006, had no personal history of TB. It took 66 days from the initial sample collection for a final laboratory report to confirm that the strain was XDR-TB, and the cost of the second-line drugs used to treat the man was NZ$10 000 per month, Dunedin Hospital Respiratory Consultant Dr Colin Wong said. "Although our experience indicates that there is potential for treatment success, definitive treatment guidelines are needed and more data are required to inform treatment and help contain spread," Dr Wong said.
"Confirming XDR-TB in a young man from Burma who had no history of previous TB treatment suggests that XDR-TB may be more common in Burma than has been widely believed, reinforcing the need for strengthening laboratory support networks and TB surveillance systems in South-East Asia."
In an accompanying editorial, infectious diseases expert Associate Professor Paul Johnson, Infectious Diseases Department, Austin Health said that while Australia was a low-risk country for XDR-TB, having recorded one case of XDR-TB in 2004 and one in 2010, a national response was needed.
That strategy must include sustaining and extending existing overseas programs that helped neighbouring countries control TB, while the next line of defence was the primary care clinician.
"Rapid diagnosis of pulmonary TB minimises secondary transmission, whatever the resistance pattern of the isolate," Professor Johnson said.
"Then we need to strengthen our local TB public health services and recognise that as TB resistance increases linearly, the cost and complexity of managing these cases increases exponentially.
"Finally, we need to keep up to date with new technology ... Molecular diagnostics are not yet perfect - we will need to retain culture-based methods for a while yet - but they are now becoming widely available and progressively cheaper.
"We need to be organised and up to date if we want to stay ahead of TB."
http://www.medicalnewstoday.com/releases/227427.php
Monday, 23 May 2011
TUBERCULOSIS: Latent tuberculosis in nursing professionals of a Brazilian hospital
Authors: Karen Gisele Person SeveroJulia da Silva OliveiraMarcelo CarneiroAndreia Rosane de Moura ValimEliane Carlosso KrummenauerLia Goncalves Possuelo
Credits/Source: Journal of Occupational Medicine and Toxicology 2011, 6:15
Tuberculosis (TB) is considered an occupational disease among health-care workers (HCWs). Direct contact with TB patients leads to an increased risk to become latently infected by Mycobacterium tuberculosis.
The objective of this study is to estimate the prevalence of latent infection by M. tuberculosis among nursing professionals of a hospital from Rio Grande do Sul, assessed by tuberculin skin test (TST).
From November 2009 to May 2010, latent infection by M. tuberculosis was assessed by the TST in 55 nursing professionals.
Epidemiological information was collected using a standardized questionnaire. A positive TST result (>or =10 mm) was observed in 47.3% of the HCWs tested.
There was no significant difference in TST positivity when duration of employment or professional category (technician or nurse) was evaluated. The results of this work reinforce the need of control measures to prevent latent infection by M.tuberculosis among nursing professionals at the hospital where the study was conducted.
http://7thspace.com/headlines/382711/latent_tuberculosis_in_nursing_professionals_of_a_brazilian_hospital.html
Credits/Source: Journal of Occupational Medicine and Toxicology 2011, 6:15
Tuberculosis (TB) is considered an occupational disease among health-care workers (HCWs). Direct contact with TB patients leads to an increased risk to become latently infected by Mycobacterium tuberculosis.
The objective of this study is to estimate the prevalence of latent infection by M. tuberculosis among nursing professionals of a hospital from Rio Grande do Sul, assessed by tuberculin skin test (TST).
From November 2009 to May 2010, latent infection by M. tuberculosis was assessed by the TST in 55 nursing professionals.
Epidemiological information was collected using a standardized questionnaire. A positive TST result (>or =10 mm) was observed in 47.3% of the HCWs tested.
There was no significant difference in TST positivity when duration of employment or professional category (technician or nurse) was evaluated. The results of this work reinforce the need of control measures to prevent latent infection by M.tuberculosis among nursing professionals at the hospital where the study was conducted.
http://7thspace.com/headlines/382711/latent_tuberculosis_in_nursing_professionals_of_a_brazilian_hospital.html
TUBERCULOSIS: Simplifying treatment for TB without symptoms
May 16 2011
The findings of a large government trial show a treatment regimen that differs from the standard therapy may be effective in treating the latent form of tuberculosis.
About 11 million people in the U.S. are infected with latent tuberculosis, which is symptom-free and is not contagious. Of those, 5 to 10 percent will go on to develop active TB, which can be spread to others and can be fatal if not properly treated.
Researchers looked at 8,000 people with latent TB, mostly in the United States or Canada. They were randomly given one of two treatments- the standard course of therapy, which takes nine months of daily treatment, or a once-weekly treatment for three months. The standard treatment is isoniazid. The experimental regimen combined isoniazid with rifapentine.
"The treatment of latent TB can be shortened from 270 doses to 12 doses, and be just as effective- that's pretty impressive," said Dr. Dean Schraufnagel, president of the American Thoracic Society and a TB expert.
Those on the once-weekly treatment were more likely to complete it- 82% versus the current rate of 69%.
"This new treatment for TB may have great, extraordinary consequences," Schraufnagel said. "I believe this will be a major strategy to control TB, both in the U.S. and worldwide."
Statistics from the CDC show the case count is on the decline, but in 2007, 544 deaths occurred from TB. In 2009, the case numbers were at an all-time low. Asians, African Americans and Native Hawaiians, along with foreign-born individuals, are disproportionately affected more than whites.
“Achieving CDC's goal of TB elimination in the United States means not only treating those individuals who already have TB disease, but also treating those with latent TB infection who are at high risk of developing TB disease and potentially transmitting it to others,” said Dr. Kevin Fenton, Director of CDC’s National Center for HIV-AIDS, Viral Hepatitis, STD and TB Prevention (NCHHSTP).
“While the number of reported cases of TB disease is currently low, in today's highly interconnected world, we need to guard against a resurgence of TB both at home and abroad,” he added.
Symptoms of TB can include chest pain, a bad cough (possibly with blood), weakness and a fever. While TB usually impacts the lungs, the kidneys, brain and spine may also be affected.
Schraufnagel said people with latent TB who go on to develop active TB won't know it at first.
"They'll develop a little cough- the cough persists," he said. "They think it might be a cold, sometimes they might have a little fever. This cough doesn't go away and after a month or two months, or three months, they may contact a doctor. And even then, they're often treated for a cold or some other thing. Then they would get an X-ray or examine the sputum and make the diagnosis of TB. By that time, those people have infected 10, 20, 30, 40, a lot of new people."
The CDC offers these guidelines as to who should get tested for TB:
- If you've been around someone with active TB disease
- If you have HIV or another condition that makes the immune system weaker
- If you live in a homeless shelter or some nursing homes
- If you are from a country where TB is very common
- If you inject illegal drugs
One-third of the world's total population are infected with TB bacteria, according to the World Health Organization.
It says each person who becomes sick with active TB, if not treated, can infect on average 10 to 15 other people a year.
"It's important to note that the study was conducted in countries which carry a low to medium incidence of tuberculosis,” said Dr. Kenneth Castro, Director, Division of Tuberculosis Elimination, NCHHSTP. "That is primarily in the United States and Canada, and the results can therefore only be applied to these settings. The trial did not include countries with high tuberculosis incidence where the increased risk of re-infection could affect the effectiveness of this regimen."
http://thechart.blogs.cnn.com/2011/05/16/simplifying-treatment-for-tb-without-symptoms/
TUBERCULOSIS: Shorter treatment found for latent tuberculosis (Priftin - Rifapentine)
Thomas H. Maugh II, Los Angeles Times thomas.maugh@latimes.com
May 17, 2011
A cocktail of antibiotics taken for three months works as well as the standard nine-month TB treatment, researchers say. That increases the proportion of people who finish treatment, helping stop the spread of TB.
In what is being hailed as the biggest breakthrough since the 1960s in treatment for latent tuberculosis — noninfectious TB without symptoms — researchers said Monday that weekly doses of a cocktail of antibiotics can cure the infection in only three months as effectively as the standard treatment of daily drugs for nine months.
By reducing the number of pills and shortening the time required for therapy, the new regimen increased the proportion of patients who completed treatment from 69% to 82%. By increasing the success rate of therapy, the regimen should reduce spread of the disease and the risk of inducing resistance to TB drugs, experts said.
"It's very clear that, in this country, if we are going to get rid of TB, we have to do so by preventing people at risk from going on to develop the disease," said Dr. Richard Chaisson of the Johns Hopkins University School of Medicine, the senior author of the study. That can only be accomplished by curing latent TB, he said.
Latent TB refers to infection by the TB bacterium in people who do not have symptoms and cannot infect others. But that latent infection can be converted into an active one by many different factors — at which point the patient becomes infectious.
Although TB control measures in the United States have brought the incidence of the disease to an all-time low of 11,181 cases in 2010, it is estimated that at least 11 million Americans have latent TB.
"The 11 million Americans with latent TB represent a ticking time bomb," Dr. Kenneth Castro, director of the Centers for Disease Control and Prevention's division of tuberculosis elimination, said at a news conference Monday. "They're the source of future TB cases."
Daily doses of the antibiotic isoniazid have been the standard of care for TB for nearly 60 years. But a newer, more potent drug, rifapentine, marketed under the brand name Priftin by Sanofi-Aventis, persists in the body for long periods.
In the study, begun 10 years ago, researchers enrolled 8,053 people with latent TB, most living in the U.S. and Canada, though some were in Brazil and Spain. Half were selected to receive conventional daily isoniazid treatment for nine months and half received a combination of isoniazid and rifapentine weekly for 12 weeks.
In the 33 months of follow-up, seven of those receiving the combination therapy developed TB, compared with 15 of those receiving isoniazid alone, coauthor Dr. Timothy Sterling of Vanderbilt University reported at the American Thoracic Society International Conference in Denver.
The combination "works certainly as well as isoniazid, and actually a little bit better," Chaisson said.
One complication is that the treatment cannot be given simultaneously with drugs for HIV infections, a significant drawback because many patients in the developing world have both diseases. Rifapentine stimulates the production of liver enzymes that break down many drugs, including protease inhibitors used for HIV treatment. The enzymes reduce levels of the drugs by as much as 95%, making use of the drugs at the same time pointless.
Chaisson said the team was now testing a regimen in which protease inhibitor treatment is halted for a month and rifapentine given daily. Normal HIV treatment is then resumed. Results from that study should be published soon.
The trial was sponsored by the CDC, and results have been submitted for publication.
http://www.latimes.com/health/la-he-latent-tb-20110517,0,2486639.story
May 17, 2011
A cocktail of antibiotics taken for three months works as well as the standard nine-month TB treatment, researchers say. That increases the proportion of people who finish treatment, helping stop the spread of TB.
In what is being hailed as the biggest breakthrough since the 1960s in treatment for latent tuberculosis — noninfectious TB without symptoms — researchers said Monday that weekly doses of a cocktail of antibiotics can cure the infection in only three months as effectively as the standard treatment of daily drugs for nine months.
By reducing the number of pills and shortening the time required for therapy, the new regimen increased the proportion of patients who completed treatment from 69% to 82%. By increasing the success rate of therapy, the regimen should reduce spread of the disease and the risk of inducing resistance to TB drugs, experts said.
"It's very clear that, in this country, if we are going to get rid of TB, we have to do so by preventing people at risk from going on to develop the disease," said Dr. Richard Chaisson of the Johns Hopkins University School of Medicine, the senior author of the study. That can only be accomplished by curing latent TB, he said.
Latent TB refers to infection by the TB bacterium in people who do not have symptoms and cannot infect others. But that latent infection can be converted into an active one by many different factors — at which point the patient becomes infectious.
Although TB control measures in the United States have brought the incidence of the disease to an all-time low of 11,181 cases in 2010, it is estimated that at least 11 million Americans have latent TB.
"The 11 million Americans with latent TB represent a ticking time bomb," Dr. Kenneth Castro, director of the Centers for Disease Control and Prevention's division of tuberculosis elimination, said at a news conference Monday. "They're the source of future TB cases."
Daily doses of the antibiotic isoniazid have been the standard of care for TB for nearly 60 years. But a newer, more potent drug, rifapentine, marketed under the brand name Priftin by Sanofi-Aventis, persists in the body for long periods.
In the study, begun 10 years ago, researchers enrolled 8,053 people with latent TB, most living in the U.S. and Canada, though some were in Brazil and Spain. Half were selected to receive conventional daily isoniazid treatment for nine months and half received a combination of isoniazid and rifapentine weekly for 12 weeks.
In the 33 months of follow-up, seven of those receiving the combination therapy developed TB, compared with 15 of those receiving isoniazid alone, coauthor Dr. Timothy Sterling of Vanderbilt University reported at the American Thoracic Society International Conference in Denver.
The combination "works certainly as well as isoniazid, and actually a little bit better," Chaisson said.
One complication is that the treatment cannot be given simultaneously with drugs for HIV infections, a significant drawback because many patients in the developing world have both diseases. Rifapentine stimulates the production of liver enzymes that break down many drugs, including protease inhibitors used for HIV treatment. The enzymes reduce levels of the drugs by as much as 95%, making use of the drugs at the same time pointless.
Chaisson said the team was now testing a regimen in which protease inhibitor treatment is halted for a month and rifapentine given daily. Normal HIV treatment is then resumed. Results from that study should be published soon.
The trial was sponsored by the CDC, and results have been submitted for publication.
http://www.latimes.com/health/la-he-latent-tb-20110517,0,2486639.story
Tuesday, 3 May 2011
TUBERCULOSIS: Sequencing Study Finds Mutations in Latent Tuberculosis Bugs
April 25, 2011 By a GenomeWeb staff reporter
NEW YORK (GenomeWeb News) – An online study in Nature Genetics yesterday hints that drug resistance may arise in tuberculosis-causing bacteria even during latent stages of infection.
A Harvard University-led team sequenced the genomes of nearly three-dozen Mycobacterium tuberculosis isolates collected from nine infected macaques. When they used SNP data to gauge mutation rates at different stages of infection, the researchers found comparable levels of mutation under each of the conditions tested. The findings suggest drug resistance — including resistance to a treatment that relies on the antibiotic isoniazid alone — can likely occur even when tuberculosis infection is not at an active stage.
"We show that [M. tuberculosis] continues to acquire mutations during disease latency," senior author Sarah Fortune, an immunology and infectious diseases researcher with the Harvard School of Public Health, and her co-authors wrote, "which may explain why isoniazid monotherapy for latent tuberculosis is a risk factor for the emergence of isoniazid resistance."
Active tuberculosis is typically tackled with a combination of different antibiotics, the researchers explained. Latent infections, on the other hand, are considered less mutation prone, and are more often treated with a lone antibiotic called isoniazid, or INH.
Nevertheless, some epidemiological studies have reported elevated INH resistance in tuberculosis-causing bugs that had been treated with this preventative monotherapy, the authors explained, raising suspicions that mutations may be more common during latency than previously appreciated — a possibility that the team explored with whole-genome sequencing.
"[W]e sought to define the mutational capacity of the bacterium during infection to better predict the rate at which drug resistance can be expected to emerge in active, latent, and reactivated disease," they wrote.
Using the Illumina Genome Analyzer, the researchers did single-read and paired-end sequencing of a M. tuberculosis strain known as Erdman and of 33 M. tuberculosis isolates from nine macaques that either had active tuberculosis infections, latent infections, or infections that were re-activated after a period of latency.
In the process, they generated sequence that covered 93 percent of each genome, on average, to a depth of about 117 times.
After tracking down variants in the genomes and verifying them with targeted Sanger sequencing, the team was left with 14 SNPs that seem to have arisen over the course of macaque infections. But rather than seeing more mutations in the isolates from macaques with active tuberculosis infections, the researchers found comparable mutation rates in each of the three infection scenarios.
"Our data indicate that in macaques with active, latent, and reactivated disease, the bacterial populations acquire mutations at the same rate over time, regardless of the number of bacterial replications that have occurred," they wrote.
Moreover, their subsequent experiments hint that these mutation rates are similar to those found when M. tuberculosis is grown in a lab setting.
The findings suggest that drug resistance is not only an issue to contend with during active tuberculosis infection, the researchers explained, since bacteria can also mutate during latent infection and in early stages of reactivation.
Those involved in the study emphasize that more research is needed to understand whether M. tuberculosis mutation patterns are similar in infected humans. Still, they say, the results underscore the need for surveillance for resistance-related mutations — particularly if preventative INH treatment becomes more broadly used to treat latent tuberculosis in some populations, including those infected with HIV.
"[INH preventative monotherapy] is now being recommended globally for HIV-positive individuals with latent tuberculosis where bacterial burden and the rate of treatment failure may be higher because of immunocompromise," the authors noted.
"If our data from the macaque model are predictive of the mutational capacity of [M. tuberculosis] in HIV-positive individuals, INH mono-resistance could arise at a substantial rate," they added. "These findings emphasize the importance of drug resistance testing and careful monitoring for treatment in these populations."
http://www.genomeweb.com/sequencing/sequencing-study-finds-mutations-latent-tuberculosis-bugs
NEW YORK (GenomeWeb News) – An online study in Nature Genetics yesterday hints that drug resistance may arise in tuberculosis-causing bacteria even during latent stages of infection.
A Harvard University-led team sequenced the genomes of nearly three-dozen Mycobacterium tuberculosis isolates collected from nine infected macaques. When they used SNP data to gauge mutation rates at different stages of infection, the researchers found comparable levels of mutation under each of the conditions tested. The findings suggest drug resistance — including resistance to a treatment that relies on the antibiotic isoniazid alone — can likely occur even when tuberculosis infection is not at an active stage.
"We show that [M. tuberculosis] continues to acquire mutations during disease latency," senior author Sarah Fortune, an immunology and infectious diseases researcher with the Harvard School of Public Health, and her co-authors wrote, "which may explain why isoniazid monotherapy for latent tuberculosis is a risk factor for the emergence of isoniazid resistance."
Active tuberculosis is typically tackled with a combination of different antibiotics, the researchers explained. Latent infections, on the other hand, are considered less mutation prone, and are more often treated with a lone antibiotic called isoniazid, or INH.
Nevertheless, some epidemiological studies have reported elevated INH resistance in tuberculosis-causing bugs that had been treated with this preventative monotherapy, the authors explained, raising suspicions that mutations may be more common during latency than previously appreciated — a possibility that the team explored with whole-genome sequencing.
"[W]e sought to define the mutational capacity of the bacterium during infection to better predict the rate at which drug resistance can be expected to emerge in active, latent, and reactivated disease," they wrote.
Using the Illumina Genome Analyzer, the researchers did single-read and paired-end sequencing of a M. tuberculosis strain known as Erdman and of 33 M. tuberculosis isolates from nine macaques that either had active tuberculosis infections, latent infections, or infections that were re-activated after a period of latency.
In the process, they generated sequence that covered 93 percent of each genome, on average, to a depth of about 117 times.
After tracking down variants in the genomes and verifying them with targeted Sanger sequencing, the team was left with 14 SNPs that seem to have arisen over the course of macaque infections. But rather than seeing more mutations in the isolates from macaques with active tuberculosis infections, the researchers found comparable mutation rates in each of the three infection scenarios.
"Our data indicate that in macaques with active, latent, and reactivated disease, the bacterial populations acquire mutations at the same rate over time, regardless of the number of bacterial replications that have occurred," they wrote.
Moreover, their subsequent experiments hint that these mutation rates are similar to those found when M. tuberculosis is grown in a lab setting.
The findings suggest that drug resistance is not only an issue to contend with during active tuberculosis infection, the researchers explained, since bacteria can also mutate during latent infection and in early stages of reactivation.
Those involved in the study emphasize that more research is needed to understand whether M. tuberculosis mutation patterns are similar in infected humans. Still, they say, the results underscore the need for surveillance for resistance-related mutations — particularly if preventative INH treatment becomes more broadly used to treat latent tuberculosis in some populations, including those infected with HIV.
"[INH preventative monotherapy] is now being recommended globally for HIV-positive individuals with latent tuberculosis where bacterial burden and the rate of treatment failure may be higher because of immunocompromise," the authors noted.
"If our data from the macaque model are predictive of the mutational capacity of [M. tuberculosis] in HIV-positive individuals, INH mono-resistance could arise at a substantial rate," they added. "These findings emphasize the importance of drug resistance testing and careful monitoring for treatment in these populations."
http://www.genomeweb.com/sequencing/sequencing-study-finds-mutations-latent-tuberculosis-bugs
TUBERCULOSIS: British screening misses most incoming latent TB
27 April 2011 by Jessica Hamzelou
London may owe its reputation as the tuberculosis capital of Europe to the UK's TB screening programme. A new study suggests the current policy for screening immigrants from countries with a known TB problem misses 71 per cent of those who carry the disease but do not display symptoms. A policy change that would cost little more could bring that number down to 8 per cent.
British policy is to X-ray people arriving from countries known to have 40 or more cases of active TB for every 100,000 people. However, X-rays are effective at identifying active infections only: individuals who don't display symptoms of disease remain undetected. "Their X-ray scans are normal," says Ajit Lalvani at Imperial College London.
Latent TB can take anywhere from a few weeks to a lifetime to develop into an active form of the disease, but around 5 per cent of carriers will develop full-blown TB within a few years, says Lalvani.
Immigrants arriving in the UK from countries with 500 or more cases of active TB per 100,000 people face a more stringent test that will detect latent TB. It involves exposing a blood sample to TB antigens. If a person's immune system has been exposed to such an antigen before, the blood's T-cells will respond by releasing a protein known as interferon gamma; otherwise, the T-cells will do nothing. People with both active and latent forms of the disease can be identified in this way.
Lalvani and his colleagues studied three busy TB screening centres in London, Leeds and Blackburn – regions with high levels of TB in the immigrant population – between 2008 and 2010. Their analysis suggested that the current rules for TB screening were missing 71 per cent of cases of latent TB, which may prove costly to treat if they develop into an active form of the disease.
£3000 per case
To find a cost-effective alternative, the group analysed the estimated costs and benefits associated with lowering the latent TB screening threshold in order to screen more immigrants. They found that by using latent-TB screening for people from countries with TB rates above 150 per 100,000 – rather than 500 per 100,000 – they would be able to catch 92 per cent of latent TB cases.
The overall cost of extending latent screening would be around £20,000 per case of TB averted – "around £3000 more per case averted than the current [screening] programme", says Lalvani. He suggests that extending latent screening this way would actually save money, because it may cost a lot more to deal with cases of full-blown TB arising from latent infections: as well as treating the patient, everyone that they have been in contact with must be screened to make sure they have not become infected, which may be expensive.
However, the group has not yet carried out a full cost analysis to confirm that extra screening is cheaper in the long run.
Journal reference: The Lancet, DOI: 10.1016/s1473-3099(11)70069-x
http://www.newscientist.com/article/dn20424-british-screening-misses-most-incoming-latent-tb.html
London may owe its reputation as the tuberculosis capital of Europe to the UK's TB screening programme. A new study suggests the current policy for screening immigrants from countries with a known TB problem misses 71 per cent of those who carry the disease but do not display symptoms. A policy change that would cost little more could bring that number down to 8 per cent.
British policy is to X-ray people arriving from countries known to have 40 or more cases of active TB for every 100,000 people. However, X-rays are effective at identifying active infections only: individuals who don't display symptoms of disease remain undetected. "Their X-ray scans are normal," says Ajit Lalvani at Imperial College London.
Latent TB can take anywhere from a few weeks to a lifetime to develop into an active form of the disease, but around 5 per cent of carriers will develop full-blown TB within a few years, says Lalvani.
Immigrants arriving in the UK from countries with 500 or more cases of active TB per 100,000 people face a more stringent test that will detect latent TB. It involves exposing a blood sample to TB antigens. If a person's immune system has been exposed to such an antigen before, the blood's T-cells will respond by releasing a protein known as interferon gamma; otherwise, the T-cells will do nothing. People with both active and latent forms of the disease can be identified in this way.
Lalvani and his colleagues studied three busy TB screening centres in London, Leeds and Blackburn – regions with high levels of TB in the immigrant population – between 2008 and 2010. Their analysis suggested that the current rules for TB screening were missing 71 per cent of cases of latent TB, which may prove costly to treat if they develop into an active form of the disease.
£3000 per case
To find a cost-effective alternative, the group analysed the estimated costs and benefits associated with lowering the latent TB screening threshold in order to screen more immigrants. They found that by using latent-TB screening for people from countries with TB rates above 150 per 100,000 – rather than 500 per 100,000 – they would be able to catch 92 per cent of latent TB cases.
The overall cost of extending latent screening would be around £20,000 per case of TB averted – "around £3000 more per case averted than the current [screening] programme", says Lalvani. He suggests that extending latent screening this way would actually save money, because it may cost a lot more to deal with cases of full-blown TB arising from latent infections: as well as treating the patient, everyone that they have been in contact with must be screened to make sure they have not become infected, which may be expensive.
However, the group has not yet carried out a full cost analysis to confirm that extra screening is cheaper in the long run.
Journal reference: The Lancet, DOI: 10.1016/s1473-3099(11)70069-x
http://www.newscientist.com/article/dn20424-british-screening-misses-most-incoming-latent-tb.html
Tuesday, 12 April 2011
TUBERCULOSIS: Community-based cross-sectional survey of latent tuberculosis infection in Afar pastoralists, Ethiopia, using QuantiFERON-TB Gold In-Tube and tuberculin skin test
Author: Mengistu LegesseGobena AmeniGezahegne MamoGirmay MedhinGunnar BjuneFekadu Abebe
Credits/Source: BMC Infectious Diseases 2011, 11:89
There is little information concerning community-based prevalence of latent tuberculosis infection (LTBI) using T-cell based interferon-gamma (IFN-gamma) release assays (IGRAs), particularly in TB endemic settings. In this study, the prevalence of LTBI in the Afar pastoral community was assessed using QuantiFERON-TB Gold In-Tube (QFTGIT) and tuberculin skin tests (TST).
Methods:
A community-based cross-sectional survey of LTBI involving 652 apparently healthy adult pastoralists was undertaken in the pastoral community of Amibara District of the Afar Region between April and June 2010.
Results:
The prevalence of LTBI was estimated as 63.7% (363/570) using QFTGIT at the cut-off point recommended by the manufacturer ([greater than or equal to] 0.35 IU/ml IFN-gamma), while it was 74.9% (427/570) using a cut-off point [greater than or equal to] 0.1 IU/ml IFN-gamma.
The QFTGIT-based prevalence of LTBI was not significantly associated with the gender or age of the study participants. However, the prevalence of LTBI was 31.2% (183/587) using TST at a cut-off point [greater than or equal to] 10 mm of skin indurations, and it was higher in males than females (36.8% vs.
23.5%, X2 =11.76; p <0.001). There was poor agreement between the results of the tests (k= 0.098, 95% CI, 0.08 - 0.13).
However, there was a positive trend between QFTGIT and TST positivity (X2 = 96.76, P<0.001). Furthermore, individuals with skin indurations [greater than or equal to] 10 mm were 13.6 times more likely to have positive results using QFTGIT than individuals with skin indurations of 0 mm (adjusted OR = 13.6; 95%CI, 7.5 to 24.7, p <0.001).
Conclusions:
There is currently no agreed gold standard for diagnosis of LTBI.
However, the higher prevalence of LTBI detected using QFTGIT rather than TST suggests that QFTGIT could be used for epidemiological studies concerning LTBI at the community level, even in a population unreactive to TST. Further studies of adults and children will be required to assess the effects of factors such as malnutrition, non-tuberculosis mycobacterial infections, HIV and parasitic infections on the performance of QFTGIT.
http://7thspace.com/headlines/378533/community_based_cross_sectional_survey_of_latent_tuberculosis_infection_in_afar_pastoralists_ethiopia_using_quantiferon_tb_gold_in_tube_and_tuberculin_skin_test_.htm
Tuesday, 5 April 2011
TUBERCULOSIS: New test can quickly distinguish infection from tuberculosis disease
Apr 2, 2011
A group of scientists have developed a potential new experimental diagnostic test that is able to quickly distinguish individuals with active tuberculosis (TB) from those with latent TB infection.
If the preliminary results of the study will be confirmed in a larger population sample, the new diagnostic system could allow more effective strategies to control the spread of the re-emerging pathology.
The work was performed by a group of scientists from the Catholic University of Rome, the National Institute of Infectious Diseases "L. Spallanzani" of Rome.
TB is an infection caused by Mycobacterium tuberculosis, the bacterium known as Koch's bacillus, named after its discoverer (Robert Koch) in 1882. Following infection with the bacillus, two different scenario may occur: "active disease", clinically evident, and that - if not properly treated - can lead to death and the so called "latent infection," that is asymptomatic and that can last for a lifetime.
"The tuberculin skin test- explains Delia Goletti, corresponding author of the paper - has several drawbacks, primarily that is unable to differentiate between infection with environmental mycobacteria (typically not dangerous to humans), vaccination with Bacillus of Calmette et Guerin (BCG) and infection with M. tuberculosis. A new assay is being used since ten years, which includes a blood test, based on specific proteins of Mycobacterium tuberculosis. The new blood test, called "Interferon - release assays (IGRA)", based on the release of interferon - in response to M. tuberculosis-specific antigens, is able to selectively identify those who have contracted TB infection.
"However - continues Goletti - IGRA, as well as the tuberculin test, are not able to distinguish people with latent TB infection compared to those with active TB disease ".
"The results of our study", said Giovanni Delogu, first author of the article, - demonstrate that it is possible to distinguish those infected from those with the disease, by simply performing an extra blood test using a protein of the bacillus named HBHA".
"In order for the test to be effective, the HBHA protein must have special features, and to date it has been difficult to obtain large amounts of this protein. - continued Delogu -. Well, our research group has developed an innovative experimental protocol to obtain large amounts of protein with limited costs, opening the possibility to use this test on a large scale ".
"In this study we have developed an innovative diagnostic algorithm, which consists of a response to the protein HBHA in combination with the IGRA and the results have shown that the response to HBHA associates with latent TB infection. This procedure allows to rapidly identify those who really need the treatment for active TB," concluded Goletti.
"The response to HBHA can be used as a biomarkers for latent TB infection and then to some extent can be considered as a response of protection to TB. It is important to understand what are the mechanisms triggered by the infection which can cause the appearance or not of the disease", said Stefania Zanetti, professor of Microbiology at the University of Sassari.
"These results - concludes the researchers - open the road to a multicenter study -- "In the future we plan to extend the study to a larger number of patients, giving priority to certain groups where diagnosing active TB can be challenging, such as immunocompromised individuals and children. We also plan to tests the new assay in countries with a high burden of TB".
The study has been published on the international journal PLoS One.
http://www.dnaindia.com/scitech/report_new-test-can-quickly-distinguish-infection-from-tuberculosis-disease_1527532
Tuesday, 18 January 2011
TUBERCULOSIS: Treating Latent TB After 65 Raises Serious Side-Effect Risk
Jan. 10 (HealthDay News) --
People over age 65 are at increased risk for serious side effects while undergoing latent tuberculosis therapy, a new study finds.
Latent tuberculosis occurs when TB bacteria lurk in the body without making the person sick. The host has no symptoms of TB and is not contagious. However, there is still a chance the bacteria could multiply and cause tuberculosis, which can be fatal if it goes untreated.
Latent TB therapy reduces the chances of developing active TB and is used in Canada and the United States as a way to control the disease. The decision to treat a patient with latent TB therapy depends on his or her risk of developing active disease and of experiencing harmful side effects, explained Dr. Dick Menzies, of the Montreal Chest Institute, and colleagues.
In a six-year study of a large population of more than 9,000 latent TB patients who were treated for tuberculosis and a matching control group that was not treated, Menzies and his colleagues found that a higher percentage of patients undergoing latent TB therapy required hospitalization for serious liver problems that those who went untreated. The excess risk was contributed largely by people over 65, he and his colleagues reported, adding that the risk remained significant even after adjusting for co-existing diseases and other factors.
"Our data suggest that the risks of therapy for latent tuberculosis infection are considerable among the elderly and should be considered very carefully before therapy is given," he and his colleagues concluded in the study.
The study was published in the Jan. 10 issue of the Canadian Medical Association Journal.
http://www.businessweek.com/lifestyle/content/healthday/648514.html
People over age 65 are at increased risk for serious side effects while undergoing latent tuberculosis therapy, a new study finds.
Latent tuberculosis occurs when TB bacteria lurk in the body without making the person sick. The host has no symptoms of TB and is not contagious. However, there is still a chance the bacteria could multiply and cause tuberculosis, which can be fatal if it goes untreated.
Latent TB therapy reduces the chances of developing active TB and is used in Canada and the United States as a way to control the disease. The decision to treat a patient with latent TB therapy depends on his or her risk of developing active disease and of experiencing harmful side effects, explained Dr. Dick Menzies, of the Montreal Chest Institute, and colleagues.
In a six-year study of a large population of more than 9,000 latent TB patients who were treated for tuberculosis and a matching control group that was not treated, Menzies and his colleagues found that a higher percentage of patients undergoing latent TB therapy required hospitalization for serious liver problems that those who went untreated. The excess risk was contributed largely by people over 65, he and his colleagues reported, adding that the risk remained significant even after adjusting for co-existing diseases and other factors.
"Our data suggest that the risks of therapy for latent tuberculosis infection are considerable among the elderly and should be considered very carefully before therapy is given," he and his colleagues concluded in the study.
The study was published in the Jan. 10 issue of the Canadian Medical Association Journal.
http://www.businessweek.com/lifestyle/content/healthday/648514.html
Monday, 3 January 2011
Tuberculosis Incidence in Prisons: A Systematic Review
Editors' Summary
Background
Every year, nearly 10 million people develop tuberculosis (TB)—a contagious bacterial infection usually of the lungs—and nearly two million people die from the disease. TB is caused by Mycobacterium tuberculosis, which spreads in airborne droplets when people with the disease cough or sneeze. Most people infected with M. tuberculosis never become ill—their immune system contains the infection. However, the bacteria remain dormant (latent) within the body, and a latent TB infection (LTBI) can cause active disease many years after the initial infection if host immunity declines. The symptoms of TB include a persistent cough, weight loss, and night sweats. Infection with M. tuberculosis can be diagnosed using the tuberculin skin test; tests for TB itself include chest X-rays and sputum cultures (in which bacteriologists try to grow M. tuberculosis from sputum samples, mucus brought up from the lungs by coughing). TB can usually be cured by taking several powerful antibiotics daily for several months.
Why Was This Study Done?
Last century, global control efforts began to reduce the incidence (number of new cases in a population in a given time) and prevalence (the number of affected people in a population) of LTBI and TB in many countries. Now, the emergence of antibiotic-resistant bacterial strains is thwarting these efforts. Consequently, it is important to identify settings where TB transmission is particularly high. One such setting is thought to be prisons. In these facilities, overcrowding, late case detection, inadequate treatment, and poor implementation of infection control measures (including incomplete segregation of people with active TB) might increase the TB transmission rate. However, it is not known how many people in prison become infected with M. tuberculosis or develop TB each year compared to the general population nor what percentage of LTBI and TB in the general population is attributable to exposure to M. tuberculosis in prison (the population attributable fraction or PAF%). Here, the researchers undertake a systematic review (a study that uses predefined criteria to identify all the research on a given topic) to investigate the incidence of TB in prisons.
What Did the Researchers Do and Find?
The researchers identified 23 studies that reported the incidence of LTBI and/or TB in prisons among both staff and prisoners. They estimated the incidence of TB in relevant general populations using World Health Organization data; estimates of the incidence of LTBI in the general population came from the studies themselves. The researchers then calculated the ratio between the incidence rates for LTBI and TB in prison and in the general population (incidence rate ratios or IRRs) for each study. For both LTBI and TB, the IRR varied widely between studies. The average IRR for LTBI was 26.4. That is, the average incidence of LTBI in prisons was 26.4 times higher than in the general population; the average IRR for TB was 23.0. The researchers also estimated the fraction of TB in the general population attributable to within-prison exposure to M. tuberculosis for each study. Again, there was considerable heterogeneity between the studies but, on average, the PAF% for TB in high-income countries was 8.5% (that is, one in 11 cases of TB in the general population was attributable to within-prison spread of TB); in middle-to-low–income countries, the average PAF% was 6.3%.
What Do These Findings Mean?
These findings suggest that the risk of LTBI and TB is at least an order of magnitude higher in prisons than in the general population and that the within-prison spread of LTBI and TB is likely to substantially affect the incidence of LTBI and TB in the general population. The accuracy and generalizability of these findings are limited by the small number of studies identified, by the relative paucity of studies from countries other than the USA, by study heterogeneity, and by assumptions made in the calculation of PAF%. Even so, these findings suggest that improvements in TB control in prisons would not only help to protect prisoners and staff from within-prison spread of TB but would also reduce national TB burdens. Further studies are now needed to identify the specific conditions in prisons that influence TB transmission so that rational policies can be developed to improve TB control in correctional facilities.
http://www.plosmedicine.org/article/info%3Adoi%2F10.1371%2Fjournal.pmed.1000381
Background
Every year, nearly 10 million people develop tuberculosis (TB)—a contagious bacterial infection usually of the lungs—and nearly two million people die from the disease. TB is caused by Mycobacterium tuberculosis, which spreads in airborne droplets when people with the disease cough or sneeze. Most people infected with M. tuberculosis never become ill—their immune system contains the infection. However, the bacteria remain dormant (latent) within the body, and a latent TB infection (LTBI) can cause active disease many years after the initial infection if host immunity declines. The symptoms of TB include a persistent cough, weight loss, and night sweats. Infection with M. tuberculosis can be diagnosed using the tuberculin skin test; tests for TB itself include chest X-rays and sputum cultures (in which bacteriologists try to grow M. tuberculosis from sputum samples, mucus brought up from the lungs by coughing). TB can usually be cured by taking several powerful antibiotics daily for several months.
Why Was This Study Done?
Last century, global control efforts began to reduce the incidence (number of new cases in a population in a given time) and prevalence (the number of affected people in a population) of LTBI and TB in many countries. Now, the emergence of antibiotic-resistant bacterial strains is thwarting these efforts. Consequently, it is important to identify settings where TB transmission is particularly high. One such setting is thought to be prisons. In these facilities, overcrowding, late case detection, inadequate treatment, and poor implementation of infection control measures (including incomplete segregation of people with active TB) might increase the TB transmission rate. However, it is not known how many people in prison become infected with M. tuberculosis or develop TB each year compared to the general population nor what percentage of LTBI and TB in the general population is attributable to exposure to M. tuberculosis in prison (the population attributable fraction or PAF%). Here, the researchers undertake a systematic review (a study that uses predefined criteria to identify all the research on a given topic) to investigate the incidence of TB in prisons.
What Did the Researchers Do and Find?
The researchers identified 23 studies that reported the incidence of LTBI and/or TB in prisons among both staff and prisoners. They estimated the incidence of TB in relevant general populations using World Health Organization data; estimates of the incidence of LTBI in the general population came from the studies themselves. The researchers then calculated the ratio between the incidence rates for LTBI and TB in prison and in the general population (incidence rate ratios or IRRs) for each study. For both LTBI and TB, the IRR varied widely between studies. The average IRR for LTBI was 26.4. That is, the average incidence of LTBI in prisons was 26.4 times higher than in the general population; the average IRR for TB was 23.0. The researchers also estimated the fraction of TB in the general population attributable to within-prison exposure to M. tuberculosis for each study. Again, there was considerable heterogeneity between the studies but, on average, the PAF% for TB in high-income countries was 8.5% (that is, one in 11 cases of TB in the general population was attributable to within-prison spread of TB); in middle-to-low–income countries, the average PAF% was 6.3%.
What Do These Findings Mean?
These findings suggest that the risk of LTBI and TB is at least an order of magnitude higher in prisons than in the general population and that the within-prison spread of LTBI and TB is likely to substantially affect the incidence of LTBI and TB in the general population. The accuracy and generalizability of these findings are limited by the small number of studies identified, by the relative paucity of studies from countries other than the USA, by study heterogeneity, and by assumptions made in the calculation of PAF%. Even so, these findings suggest that improvements in TB control in prisons would not only help to protect prisoners and staff from within-prison spread of TB but would also reduce national TB burdens. Further studies are now needed to identify the specific conditions in prisons that influence TB transmission so that rational policies can be developed to improve TB control in correctional facilities.
http://www.plosmedicine.org/article/info%3Adoi%2F10.1371%2Fjournal.pmed.1000381
Saturday, 18 December 2010
TUBERCULOSIS: Tuberculosis: threatening Australia’s borders
Tony Radford, CEO of Cellestis. (Cellestis offers a solution to curb influx of tuberculosis brought in by immigrants and refugees.)
Tuberculosis (TB) is regarded by many as a disease of the past, but as a recent tuberculosis outbreak in Australian’s customs offices shows, there is a case for modernising testing for TB in developed nations, and Melbourne-based company Cellestis offers a way to do so.
The recent scare involving six Australian customs officials who appear to have contracted a latent tuberculosis infection has called into question the current protection and testing measures. The episode also highlights that while TB infection rates in Australia are relatively low – around 1000 new cases are reported per year – we remain exposed to real risks.
Additionally, a study released last year, following a review of Victorian health department data from 1998 to 2007, found there was an increase in the number of people who were diagnosed with MDR-TB, a mutant strain that is resistant to two of the most effective antibiotics used to treat TB. Even more dangerously, resistant strains of TB exist and are becoming more common around the world, and it can’t be ignored that this disease kills one person every 17 seconds worldwide.
This recent scare focuses our attention on TB in immigrants, and rightly so. In Australia, the chances of contracting TB from an Australian-born person are very low. The infection is mostly imported – because we make no effort to stop anything but the most developed cases from entering the country.
We allow people to enter the community carrying TB infection, possibly drug-resistant, in a manner that we would never consider allowable for any animal crossing our borders. Not even considering the rising number of boats arriving on our shores – 173 illegal boats since 2008 – even legal immigrants aren’t receiving the necessary TB testing to prevent a further outbreak of the highly infectious respiratory disease.
Tools which far more accurately detect TB infection and indicate who will develop TB are now available, rendering the old-fashioned mind-set that finding TB and treating it is too hard is simply that – old and out of date. This, coupled with the rising number of immigrants coming in from countries with a high rate of TB (Asia accounts for 55 per cent and Africa accounts for 30 per cent of all TB cases), are good reasons for Australian authorities to reconsider TB control. Demands need to be made for an overhaul and upgrade in the country’s testing and protection against the infectious disease.
Australia needs to step up its action plan against TB to match the global standard of disease management. The world-wide strategy is being led by the US, which this year released new guidelines recommending that the modern IGRAs (simple blood tests known as interferon-gamma release assays, like Cellestis’ QuantiFERON) are used to test for TB, and similarly endorsed their use in screening immigrants.
Other countries that have realised they need to take a tougher stance against TB include Ireland, which recently experienced an outbreak of TB in a primary school. With a usually low rate of TB – around 480 cases a year – the outbreak has caused the country to urgently review its testing and protection methods for the disease to prevent a reoccurrence. The clearly acknowledged fact is that some countries with low rates took their eye off the ball, and now, with rising TB rates they are paying the price. Australia is in a unique position with its geographical separation, and needs to develop and enact modernised TB control guidelines in immigration to prevent a similar situation occurring on our shores.
This is to the benefit of all. Latent TB carriers will be detected and will be treated before progressing to TB disease, it is clearly to their benefit. It is not expensive to diagnose or treat latent TB infection – it is expensive to wait and treat TB disease. The current immigrant testing protocol simply does not allow for testing and treating TB infection, but relies only on chest X-ray, which can only and inefficiently detect advanced disease, not latent infection.
Why is it so? X-ray can largely avoid the embarrassment of an immigrant immediately infecting others straight after arrival, but does little to stop importing the disease. But until Australians invented interferon testing, first for cattle TB, the only method to find TB infection was the tuberculin skin test, the TST or Mantoux test.
The TST is over 100 years old, extremely subjective to measure, and very frequently produces false positives. Such an unreliable test causes undue stress, and adds extra and unnecessary pressure on the health system and economy. Doctors are often uncomfortable prescribing treatment based on such a test, and this ‘do nothing’ mindset has permeated immigration testing. Customs workers are exposed on a daily basis to possible infection, and deserve better.
Cellestis’ QuanitFERON test (QFT) is scientifically proven to be six times more accurate than the TST – that is, six times fewer people need to be treated to stop the same amount of TB – and has demonstrated that the new test offered economic advantages of time saving through the elimination of producing false positives as with the TST tests.
It is clear that despite having the possibility of virtually eliminating TB in this country, saving money while showing a shining light to the world that a country can achieve this goal with a comparative modicum of effort and thought, Australia is lagging behind other nations. We have little control over TB infection coming into the country, and little to no guideline on interferon testing for TB infection.
The federal government in fact facilitates and subsidises the import and use of the TST reagents from the USA – where the US Centers for Disease Control and Prevention recommends use of QFT as beneficial in BCG (Bacillus Calmette-Guérin) vaccinated people, which is in fact common in immigrants and those most likely to have TB infection – to compete with this Australian product.
Cellestis’ has a declared an emphatic strategy to make latent TB diagnosis and treatment the paradigm in all countries. It makes solid health and economic sense. Current world TB-control strategies have had only limited success, and it’s clear that killing latent infection before it becomes a serious disease stops further spread – and if a test with high predictive capacity for future TB such as QuantiFERON is used, this will be achieved very economically.
The World Health Organisation has published reports clearly showing that only treatment of latent TB can make any significant impact on TB disease. The outcome of effective TB control is not only to save existing carriers but to cut the chain of transmission before the situation worsens.
The Stop TB Partnership, which gathered in early October to discuss a global plan to tackle TB, predicted that up to ten million people will die of the respiratory disease in the next five years. There is little cause to think it will go away in the world, and a lot of reason to worry about antibiotic resistant strains. Although only 1000 cases are reported in Australia each year, this number is set to rise if our borders are not protected with sufficient testing, and disease protection, for immigrants.
http://www.lifescientist.com.au/article/367368/opinion_tuberculosis_threatening_australia_borders/
Tuberculosis (TB) is regarded by many as a disease of the past, but as a recent tuberculosis outbreak in Australian’s customs offices shows, there is a case for modernising testing for TB in developed nations, and Melbourne-based company Cellestis offers a way to do so.
The recent scare involving six Australian customs officials who appear to have contracted a latent tuberculosis infection has called into question the current protection and testing measures. The episode also highlights that while TB infection rates in Australia are relatively low – around 1000 new cases are reported per year – we remain exposed to real risks.
Additionally, a study released last year, following a review of Victorian health department data from 1998 to 2007, found there was an increase in the number of people who were diagnosed with MDR-TB, a mutant strain that is resistant to two of the most effective antibiotics used to treat TB. Even more dangerously, resistant strains of TB exist and are becoming more common around the world, and it can’t be ignored that this disease kills one person every 17 seconds worldwide.
This recent scare focuses our attention on TB in immigrants, and rightly so. In Australia, the chances of contracting TB from an Australian-born person are very low. The infection is mostly imported – because we make no effort to stop anything but the most developed cases from entering the country.
We allow people to enter the community carrying TB infection, possibly drug-resistant, in a manner that we would never consider allowable for any animal crossing our borders. Not even considering the rising number of boats arriving on our shores – 173 illegal boats since 2008 – even legal immigrants aren’t receiving the necessary TB testing to prevent a further outbreak of the highly infectious respiratory disease.
Tools which far more accurately detect TB infection and indicate who will develop TB are now available, rendering the old-fashioned mind-set that finding TB and treating it is too hard is simply that – old and out of date. This, coupled with the rising number of immigrants coming in from countries with a high rate of TB (Asia accounts for 55 per cent and Africa accounts for 30 per cent of all TB cases), are good reasons for Australian authorities to reconsider TB control. Demands need to be made for an overhaul and upgrade in the country’s testing and protection against the infectious disease.
Australia needs to step up its action plan against TB to match the global standard of disease management. The world-wide strategy is being led by the US, which this year released new guidelines recommending that the modern IGRAs (simple blood tests known as interferon-gamma release assays, like Cellestis’ QuantiFERON) are used to test for TB, and similarly endorsed their use in screening immigrants.
Other countries that have realised they need to take a tougher stance against TB include Ireland, which recently experienced an outbreak of TB in a primary school. With a usually low rate of TB – around 480 cases a year – the outbreak has caused the country to urgently review its testing and protection methods for the disease to prevent a reoccurrence. The clearly acknowledged fact is that some countries with low rates took their eye off the ball, and now, with rising TB rates they are paying the price. Australia is in a unique position with its geographical separation, and needs to develop and enact modernised TB control guidelines in immigration to prevent a similar situation occurring on our shores.
This is to the benefit of all. Latent TB carriers will be detected and will be treated before progressing to TB disease, it is clearly to their benefit. It is not expensive to diagnose or treat latent TB infection – it is expensive to wait and treat TB disease. The current immigrant testing protocol simply does not allow for testing and treating TB infection, but relies only on chest X-ray, which can only and inefficiently detect advanced disease, not latent infection.
Why is it so? X-ray can largely avoid the embarrassment of an immigrant immediately infecting others straight after arrival, but does little to stop importing the disease. But until Australians invented interferon testing, first for cattle TB, the only method to find TB infection was the tuberculin skin test, the TST or Mantoux test.
The TST is over 100 years old, extremely subjective to measure, and very frequently produces false positives. Such an unreliable test causes undue stress, and adds extra and unnecessary pressure on the health system and economy. Doctors are often uncomfortable prescribing treatment based on such a test, and this ‘do nothing’ mindset has permeated immigration testing. Customs workers are exposed on a daily basis to possible infection, and deserve better.
Cellestis’ QuanitFERON test (QFT) is scientifically proven to be six times more accurate than the TST – that is, six times fewer people need to be treated to stop the same amount of TB – and has demonstrated that the new test offered economic advantages of time saving through the elimination of producing false positives as with the TST tests.
It is clear that despite having the possibility of virtually eliminating TB in this country, saving money while showing a shining light to the world that a country can achieve this goal with a comparative modicum of effort and thought, Australia is lagging behind other nations. We have little control over TB infection coming into the country, and little to no guideline on interferon testing for TB infection.
The federal government in fact facilitates and subsidises the import and use of the TST reagents from the USA – where the US Centers for Disease Control and Prevention recommends use of QFT as beneficial in BCG (Bacillus Calmette-Guérin) vaccinated people, which is in fact common in immigrants and those most likely to have TB infection – to compete with this Australian product.
Cellestis’ has a declared an emphatic strategy to make latent TB diagnosis and treatment the paradigm in all countries. It makes solid health and economic sense. Current world TB-control strategies have had only limited success, and it’s clear that killing latent infection before it becomes a serious disease stops further spread – and if a test with high predictive capacity for future TB such as QuantiFERON is used, this will be achieved very economically.
The World Health Organisation has published reports clearly showing that only treatment of latent TB can make any significant impact on TB disease. The outcome of effective TB control is not only to save existing carriers but to cut the chain of transmission before the situation worsens.
The Stop TB Partnership, which gathered in early October to discuss a global plan to tackle TB, predicted that up to ten million people will die of the respiratory disease in the next five years. There is little cause to think it will go away in the world, and a lot of reason to worry about antibiotic resistant strains. Although only 1000 cases are reported in Australia each year, this number is set to rise if our borders are not protected with sufficient testing, and disease protection, for immigrants.
http://www.lifescientist.com.au/article/367368/opinion_tuberculosis_threatening_australia_borders/
Monday, 9 August 2010
TUBERCULOSIS: CDC Issues New Guidelines for TB Testing
Jun 28, 2010
The U.S. Centers for Disease Control and Prevention estimates that between 9 and 14 million Americans are tuberculosis (TB)-infected and asymptomatic -- with three-quarters remaining undiagnosed -- and at risk of progressing to a highly contagious form of TB disease. On Friday, CDC issued new and important guidelines on the detection of Mycobacterium tuberculosis infections, the causative agent of TB. In the guidelines, the agency advises that Interferon Gamma Release Assay (IGRA) blood tests are now preferred over the 100+-year-old tuberculin skin test (TST) for diagnosing TB infection in certain populations, including people who typically do not return for the necessary reading of TST results, and those who have received Bacille Calmette-Guérin (BCG) as a vaccine or for cancer therapy.
The CDC report, "Updated Guidelines for Using Interferon Gamma Release Assays to Detect Mycobacterium tuberculosis Infection -- United States, 2010," along with a companion implementation guide, appears in the June 25 issue of CDC's Morbidity & Mortality Weekly Report (MMWR, Volume 59, No. RR-5). In making its recommendations, CDC factored in TST's drawbacks, which its says include a higher risk for false positives, especially in people who have been BCG-vaccinated; irritating TB-extract that must be injected under the skin; and the need for a second doctor's visit.
According to the World Health Organization, about one person dies of TB every 17 seconds, causing nearly 2 million deaths annually. TB continues to be a contagious scourge in developing countries, and with the world shrinking rapidly due to global migration, it is a major public health threat in developed nations as well, including the United States. Each infected person represents a potential yet preventable future outbreak.
TB bacteria usually attack the lungs, but can affect any part of the body such as the kidney, spine, and brain. If not treated properly, TB can be fatal. TB bacteria is spread through the air when a person with TB disease of the lungs or throat coughs, sneezes, speaks, or sings, which may lead people in close proximity to become infected.
The populations specified by the new CDC guidelines represent a majority of those being screened for TB infection. Better, more reliable testing for TB infection is vital in order to efficiently identify the appropriate persons for treatment and thereby prevent its spread, the agency said.
http://ohsonline.com/Home.aspx
The U.S. Centers for Disease Control and Prevention estimates that between 9 and 14 million Americans are tuberculosis (TB)-infected and asymptomatic -- with three-quarters remaining undiagnosed -- and at risk of progressing to a highly contagious form of TB disease. On Friday, CDC issued new and important guidelines on the detection of Mycobacterium tuberculosis infections, the causative agent of TB. In the guidelines, the agency advises that Interferon Gamma Release Assay (IGRA) blood tests are now preferred over the 100+-year-old tuberculin skin test (TST) for diagnosing TB infection in certain populations, including people who typically do not return for the necessary reading of TST results, and those who have received Bacille Calmette-Guérin (BCG) as a vaccine or for cancer therapy.
The CDC report, "Updated Guidelines for Using Interferon Gamma Release Assays to Detect Mycobacterium tuberculosis Infection -- United States, 2010," along with a companion implementation guide, appears in the June 25 issue of CDC's Morbidity & Mortality Weekly Report (MMWR, Volume 59, No. RR-5). In making its recommendations, CDC factored in TST's drawbacks, which its says include a higher risk for false positives, especially in people who have been BCG-vaccinated; irritating TB-extract that must be injected under the skin; and the need for a second doctor's visit.
According to the World Health Organization, about one person dies of TB every 17 seconds, causing nearly 2 million deaths annually. TB continues to be a contagious scourge in developing countries, and with the world shrinking rapidly due to global migration, it is a major public health threat in developed nations as well, including the United States. Each infected person represents a potential yet preventable future outbreak.
TB bacteria usually attack the lungs, but can affect any part of the body such as the kidney, spine, and brain. If not treated properly, TB can be fatal. TB bacteria is spread through the air when a person with TB disease of the lungs or throat coughs, sneezes, speaks, or sings, which may lead people in close proximity to become infected.
The populations specified by the new CDC guidelines represent a majority of those being screened for TB infection. Better, more reliable testing for TB infection is vital in order to efficiently identify the appropriate persons for treatment and thereby prevent its spread, the agency said.
http://ohsonline.com/Home.aspx
Saturday, 10 July 2010
TUBERCULOSIS: Chicago outbreak
The number of active cases of tuberculosis in Kane County stemming from an outbreak at an Aurora homeless shelter now stands at 17 following a recent screening. The discovery of new cases has health officials preparing for a long period of monitoring to ensure the outbreak doesn't become widespread in the community at large.
A few weeks ago the county screened almost 260 people served by the Hesed House. Test results show 89 people screened had a latent, noncontagious form of the infection in addition to four newly discovered active cases.
"This is not a surprise to us," Kane County Health Department Executive Director Paul Kuehnert said. "This is actually the percentage we expected in the homeless population."
Part of the spread of the infection is being attributed to a ventilation system at the homeless shelter. Tuberculosis is a contagious bacterial infection mainly affecting the lungs, but it can spread to other organs.
The county has instituted an active preventive screening system at the shelter to protect against new infections. Homeless people found with either form of the infection are receiving daily drug treatments. The county plans to do additional mass screenings every 12 weeks until no new cases are discovered. The concentration, for now, is on Hesed House, but the county plans on working with all homeless shelters in the county to institute screenings, Kuehnert said.
Early detection is a key to preventing the spread of the infection, Kuehnert said. Although the 89 cases of the noncontagious form of tuberculosis sounds like a lot, Kuehnert said it is the version health officials prefer to see.
Active forms of the infection require lengthy periods of isolation in addition to the drug treatments. Untreated tuberculosis can be lethal.
"These 89 people cannot spread the infection, so they don't have to be isolated," Kuehnert said. "And that does help us on the overall cost of addressing this."
Kuehnert said he expects it may take as long as two years before the tuberculosis screenings reveal no new cases.
The Kane County outbreak comes at a time when the rest of the state is reporting a record low in new tuberculosis cases.
http://www.dailyherald.com/story/?id=389505&src=5
A few weeks ago the county screened almost 260 people served by the Hesed House. Test results show 89 people screened had a latent, noncontagious form of the infection in addition to four newly discovered active cases.
"This is not a surprise to us," Kane County Health Department Executive Director Paul Kuehnert said. "This is actually the percentage we expected in the homeless population."
Part of the spread of the infection is being attributed to a ventilation system at the homeless shelter. Tuberculosis is a contagious bacterial infection mainly affecting the lungs, but it can spread to other organs.
The county has instituted an active preventive screening system at the shelter to protect against new infections. Homeless people found with either form of the infection are receiving daily drug treatments. The county plans to do additional mass screenings every 12 weeks until no new cases are discovered. The concentration, for now, is on Hesed House, but the county plans on working with all homeless shelters in the county to institute screenings, Kuehnert said.
Early detection is a key to preventing the spread of the infection, Kuehnert said. Although the 89 cases of the noncontagious form of tuberculosis sounds like a lot, Kuehnert said it is the version health officials prefer to see.
Active forms of the infection require lengthy periods of isolation in addition to the drug treatments. Untreated tuberculosis can be lethal.
"These 89 people cannot spread the infection, so they don't have to be isolated," Kuehnert said. "And that does help us on the overall cost of addressing this."
Kuehnert said he expects it may take as long as two years before the tuberculosis screenings reveal no new cases.
The Kane County outbreak comes at a time when the rest of the state is reporting a record low in new tuberculosis cases.
http://www.dailyherald.com/story/?id=389505&src=5
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