Halton Region Public Health: Office of the Medical Officer of Health
Quick facts
- An equine case of Eastern Equine Encephalitis virus (EEEV) has been confirmed in a Milton horse with no history of travel, indicating local acquisition. This is the first confirmed EEEV case in an animal in Halton Region since provincial surveillance testing began in 2011.
- Hamilton Public Health recently received laboratory confirmation of a human case of EEEV (external link). There have been no human cases reported in Halton Region.
- EEEV infection is rare in humans, but can be severe. Neurological disease is associated with a high case fatality rate (30%) and often results in significant long-term disability (50-90%).
- Consider EEEV serology, as part of your work-up, in patients presenting with a fever and/or neurological symptoms, where mosquito exposure is a potential risk factor.
- There are no approved antivirals or vaccinations for EEEV in humans.
- Report any suspected or confirmed cases of EEEV causing encephalitis to Halton Region Public Health by calling 311.
Key messages for healthcare providers
- Similar to WNV, birds are the primary reservoir for EEEV. Mosquitoes can transmit the virus (external link) from infected birds to horses and humans, who are considered dead-end hosts and do not spread the virus further.
- Most cases of EEEV are asymptomatic. When symptoms do occur, the incubation period is 3-10 days (external link).
- EEEV can cause a flu-like illness (fever, chills, body aches, and joint pain) or neurologic disease, including meningitis or encephalitis.
- Neurological disease caused by EEEV may present at the onset of illness or develop after several days of febrile illness. It can manifest as meningitis and/or encephalitis, with symptoms such as headache, vomiting, seizures, paralysis and behavioural changes.
- There is no specific treatment for EEEV. Clinical management is supportive, focusing on symptom relief and seizure control.
- Serology is the preferred method to detect EEEV infection. For additional laboratory information, visit Public Health Ontario’s webpage (external link). Specimens must be sent to the Public Health Ontario Lab (PHOL) with both the General Test Requisition Form and the Vector-borne and Zoonotic Virus Testing Intake Form (external PDF).
Key messages for patients
No human vaccines against EEEV exist. Counsel patients on mosquito‑bite prevention, especially when visiting swampy areas, where EEEV is mostly found. For more information on how residents and their families can protect themselves from mosquito bites, visit halton.ca.