By Michael Smith, North American Correspondent, MedPage Today

Published: November 26, 2012

Reviewed by Robert Jasmer, MD; Associate Clinical Professor of Medicine, University of California, San Francisco and Dorothy Caputo, MA, BSN, RN, Nurse Planner

Globally, children bear a high burden of mortality and morbidity from tuberculosis and U.S. youngsters – despite low TB prevalence here – are not immune.

In two studies online in Pediatrics, U.S. and Chinese researchers paint striking pictures of TB among children, in both low- and high-prevalence settings.

The studies "remind us of the ongoing scourge of this ancient disease in both high- and low-prevalence countries," commented Jeffrey Starke, MD, of Baylor College of Medicine in Houston, and colleagues in an accompanying commentary article.

And they "reveal what happens when prevention strategies are inadequately addressed," Starke and colleagues argued.

In the U.S., much of childhood TB is associated with the global epidemic of the disease, reported Carla Winston, PhD, and Heather Menzies, MD, of the CDC in Atlanta.

Newly available surveillance data show that about 75% of new cases of TB among those under 18 are linked epidemiologically with foreign countries, the researchers reported.

Only 25% of the affected children – a total of 2,660 in 2008 through 2010 – had no known international connection through family or residence history, Winston and Menzies found.

The findings are based on reports to the CDC's National TB Surveillance System from 2008 to 2010 and include data -- available for the first time in 2009 -- on the parent or guardian countries of origin and history of having lived internationally for TB patients under 15.

The authors found that affected children and adolescents made up 7% of all TB cases reported annually, but the absolute numbers fell from 977 in 2008 to 865 in 2009 and 818 in 2010.

They also found that 31% of the total children diagnosed with TB were born outside the U.S., with Mexico being the most frequently reported country of foreign birth.

In addition, 52% of foreign-born patients were adolescents, ages 13 to 17 who, on average, had lived in the U.S. more than 3 years before the diagnosis of TB.

Among U.S.-born patients younger than 15, 66% had at least one foreign-born parent, more than three times the rate in the population as a whole.

The researchers cautioned that some data are missing, including such things as current living situations and contacts with international visitors.

Nevertheless, they argued, the findings suggest four groups in which prevention efforts could be enhanced: native-born children with foreign-born parents, foreign-born children with U.S.-born parents, foreign-born adolescents, and U.S.-born children in groups traditionally at risk for TB.

In China, as in most countries, childhood TB reflects recent transmission within the community, according to Adong Shen, PhD, of Beijing Children's Hospital in Beijing, and colleagues.

But data on the incidence of childhood TB in China and its clinical features are inadequate, Shen and colleagues noted.

To help fill the gap, they conducted a retrospective analysis of 1,212 children and adolescents under 18, who were admitted to Beijing Children's Hospital for TB from January 2002 to December 2010.

Overall, they found that 81.6% of patients were successfully treated.

Also, more than half of the patients (54%) had extrapulmonary disease, 38.8% had tuberculous meningitis, and 31.3% had disseminated TB.

Extrapulmonary disease was more common among patients younger than 5 and among those from rural areas.

Also, infants younger than 1 were more likely to have severe TB -- defined as tuberculous meningitis and disseminated TB -- versus less severe forms of disease.

Severe TB was associated with no bacille Calmette-Guérin vaccination and a contact history at home.

Finally, poor treatment outcomes, which was defined as failure to improve or death, were more common among those younger than 1 and those with severe TB.

They cautioned that the Beijing Children's Hospital, as a referral center, tends to have more severe cases, which might have led to sampling bias. Also, they did not analyze factors such as delay in diagnosis, poor compliance, incorrect diagnosis, and multidrug-resistant TB.

Nonetheless, the study suggests that prevention and health care efforts in a high-prevalence setting such as China -- should be aimed at patients younger than 1 as well as those with extrapulmonary disease and severe TB.