Malaria incidence among US military lowest in 9 years

The Armed Forces Health Surveillance Center has reported that 38 US service members were diagnosed with malaria in 2012, which is the lowest number of malaria cases seen in 1 year among service members for the past 9 years, according to the 2012 Malaria Update published in Medical Surveillance Monthly Report.

“The large decrease in malaria was surprising,” CAPT Kevin Russell, MD, executive director of the Armed Forces Surveillance Center, told Infectious Disease News. “In general, the expectation had been that the 2012 numbers would have been similar to those of the recent past and that any decrease or increase would have been modest.”

From 2004 to 2012, malaria surveillance was conducted among active and reserve component members of the US military. Researchers used the Defense Medical Surveillance System to identify diagnoses of malaria. They then determined the locations where the malaria acquisition had likely occurred.

Half of the cases of malaria were caused by Plasmodium vivax and 16% were caused by Plasmodium falciparum. The remainder of the cases had an unspecified responsible agent. Twenty-four of the cases (63%) were likely acquired in Afghanistan, seven (18%) cases were likely acquired in Africa and three infections (8%) were considered to have been acquired in Korea. Except for one case acquired in Honduras, the remainder of the cases had unknown area of acquisition.

“The possible reasons for the decline in cases are numerous, but it is not feasible to pinpoint which specific factors may have played a role, or the extent of their individual contributions,” Russell said.

Some of the possible reasons, according to Russell, include: diminished numbers of service members at risk of exposure; changes in environmental factors that affect the size of the population of mosquito vectors and the issuance of combat uniforms with permethrin impregnated into the fabric, among other reasons.

In a study published in the same issue of Medical Surveillance Monthly Report, researchers identified 16 laboratory-confirmed cases of malaria among active component US Army personnel from January to September 2012. Twelve of the 16 cases were due to P. vivax, one was attributed to P. falciparum and the remaining cases were unspecified, but likely due to P. vivax. Fourteen of the service members were either currently deployed in Afghanistan or had returned from Afghanistan within 9 months before diagnosis. The remaining two likely acquired the disease in Africa and Korea.

“The guidance given about malaria [to service members] covers the facts that malaria is endemic in the areas of operations, that mosquitoes are the vectors of concern and that each individual shares the burden of responsibility to protect him or herself,” Russell said. “Military unit commanders and other leaders should reinforce such guidance.”

For more information:

Armed Forces Health Surveillance Center. MSMR. 2013;20:2-5.

Shaha D. MSMR. 2013;20:6-9.