Table 10.11-1. Factors increasing the risk of JEV in travelers according to ACIP

Duration of travel

– The incidence of JE is the highest among long-term travelers

– No specific duration of travel has been identified that would be associated with increased risk of JE, but long-term stay in endemic regions increases the likelihood of exposure to bites of an infected mosquito

– Long-term travels also include frequent shorter stays in regions endemic for JE

Season of the year

In some regions of Asia JEV transmission is seasonal whereas in others it occurs all year round


– The highest risk is associated with stays in rural (agricultural) areas

– The mosquitoes that transmit JE typically breed in freshwater reservoirs, flooded rice fields, and wet areas

– JE was also reported in travelers who stayed at the seaside, in the neighborhood of rural areas or rice fields

– Large, focal outbreaks of JE indicate intensive JEV transmission in the area

Traveler’s activities

– The mosquitoes that carry JE are typically active outdoors, from dusk to dawn, hence the increased risk of exposure in travelers planning activities such as camping, trekking, biking, rafting, fishing, hunting, or staying at farms

– Staying outdoors, particularly at night, increases the risk of JE


Accommodations in nonscreened rooms without air conditioning or bednets increase the risk of bites by infected mosquitoes

Adapted from CDC. Recommendations and Reports. 68(2);1-33.

ACIP, Advisory Committee on Immunization Practices; JE, Japanese encephalitis; JEV, Japanese encephalitis virus.