Methods: TravMil is a prospective observational study enrolling subjects presenting to 5 military travel clinics. We analyzed surveys and paired sera from travelers to this region between December 2013 and May 2015. CHIKV acquisition was determined by enzyme-linked immunosorbent assay, plaque reduction neutralization test, and polymerase chain reaction.
Results: 277 travelers enrolled (51% male, median age 40 years, 43% active duty [AD]), including 10 who enrolled post-travel. The median trip duration was 10 days. 41% traveled to Mexico/Central America, 31% to South America, and 28% to the Caribbean. 51% traveled on vacation, 29% for missionary work, and 26% for a military purpose; 10% were visiting friends/relatives (VFR). 48% of travelers reported using N, N-diethyl-m-toluamide (DEET) often, 28.5% rarely, and 23.5% never; 11% used permethrin. 64% of travelers reported seeing mosquitoes; 47% reported no mosquito bites, while 6% reported >15 bites.
In a multivariate logistic regression model, AD status (odds ratio/OR 2.6 [1.3-5.4]) and increased frequency of DEET use (OR 3.3 [2.2-5.0]) were associated with seeing mosquitoes. Older age was associated with fewer mosquito bites (OR 0.97 [0.95-0.99]) in a separate multivariate logistic regression model.
Paired sera were available for CHIKV testing in 31 travelers. Three acquired CHIKV; all enrolled as ill returning travelers. All were VFR in the Caribbean and reported DEET use; none used permethrin.
Conclusion: Mosquito exposures are common in travelers to CHIKV-outbreak regions in the Americas; AD military and younger travelers may be at higher exposure risk. Self-reported PPM use is suboptimal even after pre-travel counseling. However, CHIKV acquisition was seen only in individuals who enrolled after becoming ill and reported VFR; subclinical illness was not identified in our cohort. Pre-travel counseling should target higher risk groups, including AD military, younger travelers, and those who are VFR.
T. Myers, None
K. Telu, None
M. Fairchok, None
A. Ganesan, None
M. Johnson, None
A. Kunz, None
D. Tribble, None
T. Lalani, None
H. Yun, None