The first study to quantify the effects of human migration on malaria incidence on a global scale has been published — and could lead to more effective strategies for eliminating the disease, say scientists.
Prompted by evidence that eliminating malaria in a single country is not possible if there is a steady influx of infected people from neighbouring countries, researchers mapped rates of migration and malaria transmission within and between global regions. Their work is published in Proceedings of the National Academy of Sciences (PNAS) this week (21 June).
Using migration data, transmission maps for the malaria parasite Plasmodium falciparum and global population databases the researchers identified groups of countries that were more strongly affected than others by high levels of population, and therefore infection, movement.
These groupings include countries in western and north-central Africa; central American countries where P. falciparum malaria is endemic; and countries in West and East Asia.
The researchers found that some countries, such as Ethiopia, Myanmar, China, Iran and Afghanistan, are more isolated. In these cases a nationally focused control or elimination programme stands a better chance of success.
The study also identified which nations are likely to be net exporters and importers of P. falciparum. In Africa, Mali, Burkina Faso and Niger are net migrant exporters, principally to West Africa, whereas low-transmission countries, such as Mauritania and Senegal, are receiving more malaria-infected migrants than they release.
Andrew Tatem, a researcher at the Emerging Pathogens Institute at the US-based University of Florida, and a co-author of the study, said that this is the first attempt to quantify the effects of human migration on malaria infection on a global scale.
Although there have been occasional similar studies "the datasets we used on malaria transmission and migration patterns have only recently been constructed, so it wasn't possible to examine the evidence on such a large scale before," he said.
Carlos Guerra, from the Ecuadorian Biotechnology Corporation and the Malaria Atlas Project of the UK's University of Oxford, said that the study enabled evidence-based guidelines for the design of more effective malaria-control strategies.
Countries that are connected by the flow of population and infection are already starting to work together. Examples include the Asia Pacific Malaria Elimination Network, the E8 group of eight southern African countries and PAMAFRO, a malaria reduction project between Ecuador, Colombia, Peru and Venezuela.
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