Zika Virus and Travelers: Review of Confirmed Zika Virus Cases in San Diego County, 2016

BACKGROUND: In the continental US, the vast majority of confirmed Zika virus cases are associated with travel. However, limited information exists about the characteristics and risk factors of these travelers. Such information is needed to guide targeted public health interventions for higher risk populations to help reduce the risk of disease importation and prevent local Zika virus transmission. Travelers visiting relatives and friends (VRF travelers) are known to take fewer precautions against mosquito bites during travel, therefore, possibly at greater risk of contracting Zika when traveling.

METHODS: Confirmed Zika virus cases reported to San Diego County in 2016 were analyzed to describe their social demographics, likely country of exposure and main reason for travel.

RESULTS: Preliminary results indicate that among 70 confirmed Zika virus cases in San Diego County, the median age was 32 years (range = 3-71 years) and 39 (56%) were female; 7 % were pregnant. Travel to Mexico was reported in 39% of cases; 26% traveled to Central America, 21 % to the Caribbean, 7% to South America, 4% to other counties, and 3% unknown. Among males, the highest proportion was in persons 20–39 years (51%); similarly for females, the highest proportion was among 20-39 years (56%). In all age groups, females accounted for the majority of cases. Approximately 57% of cases reported the United States as country of birth, 36% were foreign-born, and 7% unknown. Foreign-born travelers were disproportionately represented compared to total foreign-born population in the county (23.5%). Primary language reported was English (76%), followed by Spanish (19%), 4% other and 1 % unknown. Visiting family and friends as a reason for travel was observed among 34.3% of cases. Other reasons of travel included tourism/work (57.1%), and unknown/no-travel reasons (8.6%).

CONCLUSIONS: This evaluation helped identify groups among Zika travel cases, including female travelers, VRF, and foreign-born persons. Public health messaging targeted towards female, foreign-born, and VRF travelers to areas with Zika virus activity could help reduce the incidence of imported infections and subsequent risk of adverse pregnancy outcomes. In jurisdictions where imported cases are common, Zika virus surveillance should include collection of reason for travel to optimize risk communication and to engage the community in preparing and responding to Zika transmission.