Tick-borne encephalitis surveillance in U.S. military service members and beneficiaries, 2006-2018

The risk of tick-borne encephalitis (TBE) among U.S. military service members and beneficiaries residing in or traveling to Europe has not been assessed since the 1990s. The primary objective of this study was to assess the current risk of TBE in this population. Records of reportable medical events, inpatient and outpatient care, and laboratory test results were searched for TBE cases between 2006 and 2018. There were 8 individuals who met the case definition for TBE over the 13-year interval; 7 cases occurred during 2017 or 2018. Outpatient records did not identify any additional verified cases of TBE but revealed a large number of misclassified diagnoses. The risk of TBE among U.S. military service members and beneficiaries is low but may have increased in recent years. Military members and their dependents residing in Europe or Asia generally have a risk for TBE similar to that of other residents of the host nation. Additionally, there may be locations or activities that place certain individuals or units at increased risk for TBE, thus warranting additional control measures such as active surveillance, enhanced personal protective measures, and vaccination.