Malaria Incidence in US Military Families Is Related to Service Member's Birthplace

Background. Foreign-born persons make up approximately 5% of the United States military active duty service members. Studies in the general population show that travelers visiting friends and relatives have an increased risk of malaria acquisition. We hypothesized a higher incidence of malaria within the Military Health System (MHS) for those with a familial connection to malaria-endemic countries. Methods. We performed a retrospective cohort study of all service members and their family members enrolled in the MHS between October 2012 and September 2018. Participants were allocated into 2 groups according to the service member's country of birth: malaria-endemic country or nonendemic country. Malaria cases were identified by International Classification of Diseases code and annual incidence rates were calculated based on service member's birth world region. Incidence rate ratios (IRRs) compared the 2 groups. Results. Two hundred eighty-one cases of malaria were identified during the 6-year study period. The malaria-endemic group (n = 67) had 5 times the risk of malaria than the nonendemic group (n = 214) (IRR, 5.2 [95% confidence interval, 2.4–10.4]). Incidence remained higher for the malaria-endemic group even when stratified by service member and family member status. Those connected to the sub-Saharan Africa region had an average annual incidence rate of 42 cases per 100 000 persons, accounting for 86.6% of all malaria-endemic cases. Only 48% of all cases sought pretravel medical counseling. Conclusions. There was a >5 times higher incidence of malaria in the malaria-endemic group, highlighting their increased incidence of travel-related infectious diseases despite universal health insurance coverage and access to pretravel medical care.