Eastern Equine Encephalitis Virus (EEEV)

Last updated: April 24, 2023 

What is Eastern Equine Encephalitis Virus (EEEV)?

EEEV is a mosquito-borne virus than can be passed to humans and horses through mosquito bites. Person-to-person transmission is not currently known to occur. EEEV can cause severe illness in humans. To date, there have been no recorded human cases of EEEV in Ontario, however equine infections occur sporadically. As this pathogen has been detected in Canada, mosquito bite prevention is necessary to lower the risk of disease transmission.  

Who is at risk for Eastern Equine Encephalitis Virus?

Risk groups have not yet been determined for EEEV in Ontario. However, EEEV is detected more often in rural areas located close to bogs and wetlands, than in urban areas.  

What are Symptoms of Eastern Equine Encephalitis Virus?

Human cases of EEV may have similar symptoms as West Nile Virus including fever, headache, body aches, rash and potential neurological symptoms. A high fatality rate is associated with the development of encephalitis. In equine cases, development of neurological symptoms is generally followed by fatality within 48 hours in  greater than 70% of cases. 

How is Eastern Equine Encephalitis Virus monitored?

In Ontario, temporary enhanced surveillance of EEEV may occur locally after detection of an equine EEEV case. Typical routine testing is difficult as mosquito traps do not usually attract the mosquito species thought to carry EEEV.  

Additional Resources

Eastern Equine Encephalitis Virus: History and Enhanced Surveillance in Ontario (Public Health Ontario)