The United States has highly variable mosquito seasons by region. The Gulf Coast and southern states have activity from March through November, while northern states have shorter seasons from May through September. Florida, Texas, Louisiana, and Hawaii have the highest mosquito-borne disease risk. The Southwest and mountain states have minimal activity.
West Nile virus is the primary concern, with seasonal circulation across much of the country. Dengue fever occurs locally in southern Florida, Texas, and Hawaii at moderate levels. Zika caused a local outbreak in Miami in 2016. St. Louis encephalitis, western equine encephalitis, and Eastern equine encephalitis also circulate.
Culex pipiens and Culex quinquefasciatus are the main West Nile virus vectors. Aedes aegypti is present in the southern states and transmits dengue and Zika. Aedes albopictus (Asian tiger mosquito) has expanded across the eastern United States. Culex tarsalis is the primary vector in the western states.
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Disease presence data is sourced from WHO, CDC, ECDC, and OpenDengue. This is not medical advice — consult a travel health professional before your trip.