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 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.