Arboviruses cause systemic illness, often with central nervous system involvement. They are transmitted to humans by arthropods, including certain species of ticks and mosquitoes that acquire the virus while feeding on infected wild birds and small mammals. Western equine encephalitis (WEE), St. Louis encephalitis (SLE), and West Nile virus (WNV) are examples of mosquito-borne arboviral diseases that have occurred in Washington state.

International travelers to certain countries (particularly tropical areas) are at risk of Japanese encephalitis, yellow fever, dengue fever, chikungunya, and Zika virus, which emerged in many Central and South American countries in 2015.

Arboviruses are typically not spread from person to person, but in rare cases WNV has been spread through blood transfusions, organ transplants, breastfeeding, and perinatally. Zika virus can be transmitted through sexual contact, and during pregnancy and delivery from mother to baby.

Resources for the general public

• Arboviral Encephalitides, CDC
• Chikungunya Fever, CDC
• Dengue Fever, CDC
• West Nile virus, King County
• Yellow Fever, CDC
• Yellow Fever vaccine, King County

Resources for health care professionals

• Arboviral diseases are reportable conditions in King County: See disease reporting requirements
• West Nile virus information and guidance for clinicians, CDC
• Zika virus information and guidance for health care providers (scroll midway down page Zika page)