Researchers Andrew Tatem and Christina Chiyaka found that those countries that have eliminated malaria have maintained their malaria-free states with remarkable stability, going against traditional theory. Between 1945 and 2010, 79 countries eliminated malaria and 75, or 95 percent, remained malaria-free, shrinking the geographic range of the disease, the researchers said.
For the 99 countries with endemic malaria today, the research by Tatem and his colleagues has important implications for tackling the problem. The elimination of malaria may be less costly to achieve and maintain than previously thought, Tatem said.
"Traditional theory suggests that we have to get rid of malaria completely, all across the world, all at around the same time, to keep new cases from being imported and starting outbreaks in elimination countries all over again," said Tatem, who conducted the research at UF and now is a professor at the University of Southampton in the United Kingdom. Chiyaka also has moved to the United Kingdom with her family.
The researchers found, however, that malaria elimination may be a "sticky state", meaning that once elimination is achieved, resurgence becomes a rare event.
"For instance, the United States imports 1,500 cases of malaria per year but has seen very few local outbreaks resulting from these, despite still having mosquitoes capable of spreading malaria," Tatem said. "The United States doesn't have active control measures in place, but does have a well-functioning detection system in place to take care of it."
Tatem said that many factors, working in combination, have likely contributed to the stability of malaria elimination seen in many countries. These include urbanization, which creates environments that are unfavorable for malaria-spreading mosquitoes; improvements in surveillance within health systems to ensure that imported cases are treated promptly and any local outbreaks are controlled early; and travel patterns, with travelers who bring in infections from elsewhere rarely ending up in rural areas where mosquito densities are highest, thus reducing the likelihood of onward spread.
Malaria has long been a global health issue. In 1955, the World Health Organization launched an eradication campaign that eliminated the disease in many temperate and subtropical regions but did not achieve worldwide eradication. The program was scrapped after less than two decades in favor of controlling malaria. However, WHO attributed about 660,000 deaths to the disease in 2010, mostly African children.