MEDICAL ADVISORY: First Human Case of West Nile Virus (WNV)

Issued by: Dr. Jessica Jackman, MD MPH FRCPC FACPM DipABLM, Associate Medical Officer of Health

Date: September 18, 2024

Niagara Region Public Health (NRPH) has reported its first laboratory-confirmed human case of West Nile virus (WNV) infection of 2024. 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 is three to 14 days after infected mosquito bite
Only 20 percent of people will develop symptoms
Mild symptoms of WNV can include:
- Fever
- Myalgia
- Arthralgia
- Headache
- Nausea and vomiting
- Lymphadenopathy
- Maculopapular rash
About one in 150 infected people will have a severe infection, including:
- Headache / high fever
- Neck stiffness
- Disorientation
- Coma / unconsciousness
- Tremors / convulsions
- Muscle weakness / paralysis

Diagnosis and Management

Consider testing for West Nile Virus (WNV) in patients with the symptoms listed above and recent mosquito exposure.

Testing information can be found on the Public Health Ontario West Nile Virus – Serology and PCR webpage.

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 suspect or confirmed case of WNV, report it to Public Health by the next business day:
Call 905-688-8248 ext. 7330 (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

Use insect repellants containing DEET or Icaridin, especially during mornings and evenings
Wear long sleeves, pants, and socks to limit bites
Ensure open windows/doors have intact insect screens
Drain standing water on one’s property to prevent mosquito breeding

More Information

For further information, please contact NRPH, Infectious Disease program at 1-888-505-6074 or 905-688-8248 ext. 7330 Monday to Friday 8:30 a.m. to 4:30 p.m. or visit our website
West Nile Virus Surveillance Tool - Public Health Ontario
West Nile Virus - For Health Professionals - Government of Canada