Medical Advisory: First Human Case of West Nile Virus (WNV) 2026

Issued by: Dr. Hamidah Meghani, MPH, MMgt, FRCPC, Associate Medical Officer of Health
Date: September 9, 2026

Niagara Region Public Health (NRPH) has reported its first laboratory-confirmed human case of West Nile virus (WNV) infection of 2026. NRPH requests that health care professionals consider WNV illness in patients that present with compatible symptoms and recent exposure to mosquitos.

Clinical Presentation

Average incubation period ranges from two to 14 days after infected mosquito bite
Most WNV infections are asymptomatic. Approximately 20% of infected people develop symptoms. The risk of severe illness is higher among older adults and people with weakened immune systems or certain underlying health conditions.
Symptomatic individuals may develop a mild febrile illness with symptoms such as fever, headache, myalgia, arthralgia, nausea, vomiting, rash, or swollen lymph nodes. In rare cases, WNV can cause neuroinvasive disease, including meningitis, encephalitis, or acute flaccid paralysis.

Testing and Management

Testing for WNV infection is indicated in individuals with clinically compatible signs/symptoms of infection AND relevant exposures
Testing information can be found on the Public Health Ontario West Nile Virus – Serology and PCR webpage
- Reminder: submission of the new Vector-borne and Zoonotic Virus Testing Intake Form is mandatory, along with the General Test Requisition when requesting specific vector-borne or zoonotic virus tests. Specimens received without the appropriate forms are subject to cancellation
- Management is primarily supportive, there is no specific treatment, medication, or vaccine for WNV

Reporting

WNV is reportable to the Medical Officer of Health under Ontario Regulation 135/18 and amendments of the Health Protection and Promotion Act. If you have a suspect or confirmed case of WNV, contact Public Health by the next business day:

Call 905-688-8248 ext. 7590 (Mon-Fri, 8:30 a.m. to 4:30 p.m.)
Toll free: 1-888-505-6074
After-hours: 905-984-3690

Prevention Advice for Patients

Wear light-coloured long-sleeved shirts, long pants, hats, socks and shoes when outdoors
Use insect repellents that contain DEET, Icaridin, or other approved ingredients at all times of the day. Always read and follow label directions.
Drain areas of standing or stagnant water around the home where mosquitoes may breed (e.g. bird baths, old tires, buckets, toys, flowerpots etc.)
Ensure all windows and doors in your home have screens that are in good condition
Clean eavestroughs and gutters, ensuring proper drainage, and drain pooling water from low-lying areas

More Information

For further information, please contact NRPH, Environmental Health program at 1-888-505-6074 or 905-688-8248 ext. 7590, Monday to Friday 8:30 a.m. to 4:30 p.m. or visit our website.