First human case of West Nile virus reported this season
The confirmation follows the detection of West Nile virus in mosquito pools collected in Woodstock and Tavistock through SWPH's routine mosquito surveillance program. West Nile virus activity typically increases during the summer months, with most locally acquired human infections occurring in August and September. Earlier this season, WNV was detected in mosquito pools collected on July 23, 2026, confirming virus activity within the region.
Residents are reminded to protect themselves against mosquito bites and to remove standing water from their properties to help prevent mosquito breeding.
"West Nile virus is present in our region, and this first human case is an important reminder to take precautions against mosquito bites," said Dr. Ninh Tran, Medical Officer of Health at Southwestern Public Health. "Using insect repellent, covering exposed skin, and removing standing water around your home are simple steps that can significantly reduce your risk of infection."
Most people infected with West Nile virus do not develop symptoms. Approximately 80 per cent of infections are asymptomatic. Others may develop West Nile fever, a mild illness characterized by symptoms such as fever, headache, muscle aches, fatigue, rash, swollen lymph nodes, nausea, vomiting, diarrhea, eye pain, or sensitivity to light. Less than one per cent of infected individuals develop severe neurological illness, including meningitis, encephalitis, or acute flaccid paralysis.
Across Ontario, 167 human cases of West Nile virus were reported in 2025, compared with 77 cases in 2024, highlighting the importance of prevention and awareness during mosquito season. While WNV-positive mosquito pools have been identified locally in recent years, this is the first human case reported to Southwestern Public Health since 2018.
Take precautions to avoid mosquito bites:
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Use an insect repellent containing DEET or Icaridin, following label directions
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Wear light-coloured clothing, long sleeves, and long pants when outdoors, particularly at dawn and dusk when mosquitoes are most active
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Avoid areas with high mosquito activity where possible
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Avoid areas with high mosquito activity where possible
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Ensure window and door screens are in good repair
Reduce mosquito breeding sites around your property:
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Empty standing water from containers such as buckets, flowerpots, toys, wheelbarrows, and bird baths at least once a week
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Clean and maintain eavestroughs and drainage areas
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Cover or properly maintain rain barrels
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Keep swimming pools and decorative ponds properly maintained
SWPH continues to monitor West Nile virus activity through its mosquito surveillance program and encourages residents to take preventive measures throughout mosquito season.
For more information about West Nile virus and how to protect yourself, visit our website.
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