Background
Microbiology
- Virus in the Togaviridae family and Alphavirus genus
Epidemiology
- Mosquito-borne avian infection carried by the Culiseta melanura mosquito
- Horses and humans are dead-end hosts, infected by bridge vectors including Aedes vexans and Coquillettidia perturbans
- Usually only a handful of human cases annually in North America, and only one human case ever recorded in Ontario
Clinical Manifestations
- Most are asymptomatic
- Incubation period of 4 to 10 days
- For those who develop disease, it usually begins with an influenza-like illness, with fever, malaise, arthralgia, and myalgia, which lasts one to two weeks
- Some people develop neurologic disease during the febrile illness, which may progress to encephalitis
- There is a high mortality rate among those who develop encephalitis, with death usually occuring between 2 and 10 days after illness onset
- It is possible to have permanent and severe neurologic sequelae
