Eastern Equine Encephalitis Virus reported in Hamilton resident

HAMILTON, ON – On August 28, 2025, City of Hamilton Public Health Services received laboratory confirmation of a human case of Eastern Equine Encephalitis (EEE). The case is an adult resident of Hamilton, with no known history of travel. This is the first human case of EEE reported to Hamilton Public Health Services in 2025. 

EEE is transmitted through a virus that is typically found in wild birds, however humans and/or horses bitten by an infected mosquito can become ill with EEE. Hamilton Public Health Services has received confirmation of two horse cases of EEE in 2025, including the case confirmed on August 18, 2025. 

Symptoms of EEE in people usually appear three to ten days after an infected mosquito bites a person. Most people bitten by an infected mosquito won’t have any symptoms. Others will only get a mild flu-like illness with fever, headache and fatigue. Severe cases of EEE involve encephalitis (an inflammation of the brain), which starts with a sudden headache, high fever, chills and vomiting. 

Take precautions to avoid being bitten by mosquitoes

• Use a mosquito repellent (bug spray) containing DEET or Icaridin. 
• Avoid areas where mosquitoes are known to be present or cover up by wearing light coloured clothing with long sleeves and long pants when in mosquito areas such as wooded areas, on the golf course, or in the garden, especially at dawn and dusk when mosquitoes are most active.
• Reduce mosquito breeding sites by removing standing water at least weekly from your property. Mosquitoes lay their eggs in very shallow standing water. If you remove the standing water, they cannot lay eggs.
• Horses can and should be vaccinated against EEE and West Nile Virus.

Hamilton Public Health Services continually assesses the risk for human illness as part of a comprehensive vector-borne disease surveillance and prevention program. The City is currently completing its third round of mosquito larvicide treatments on city street catch basins, in addition to treatment of surface waters on public land. 

“While the risk of being infected with Eastern Equine Encephalitis (EEE) virus is low, residents should take precautions to avoid illness spread by mosquitoes,” said Dr. Bart Harvey, Associate Medical Officer of Health. “Employing simple preventive measures such as using insect repellent containing DEET or Icaridin, covering up, and removing standing water on your property to prevent mosquito breeding will reduce your risk while you enjoy the outdoors. The risk of these infections will drop once there is a heavy frost that reduces the number of mosquitoes.”

For additional information on the City’s mosquito control program, visit www.hamilton.ca/westnile or call 905-546-2489.

Additional Resources

• Web page: Eastern Equine Encephalitis Virus - Centers for Disease Control and Prevention
• Web page: Controlling mosquitoes on rural and farm properties - Ontario.ca
• Media Release: First horse case of EEE Virus reported in Hamilton since 2019 (August 19, 2025)
• City of Hamilton By-Law: Standing Water at Specified Times of the Year
• Web page: West Nile Virus