MEDICAL ADVISORY: Heightened Surveillance for West Nile Virus (WNV)

Issued by: Dr. Azim Kasmani, MD MSc FRCPC, Medical Officer of Health

Date: July 24, 2024

Niagara Region Public Health and Emergency Services' mosquito trapping and testing has confirmed the first West Nile Virus (WNV) positive mosquito pool of the year by lab result. This is the first positive testing pool since the annual monitoring season began on June 1, 2024. While there have been no reported human WNV cases in Niagara this year, health care professionals should be on heightened surveillance during active mosquito season.

Clinical Presentation

Average incubation period ranges from three to 14 days after infected mosquito bite
Only 20 percent of people will develop symptoms
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:
- High fever
- Neck stiffness
- Disorientation
- Loss of consciousness
- Tremors
- Convulsions
- Muscle weakness

Testing and Management

Consider testing for WNV in patients with the symptoms listed above AND recent mosquito exposure – especially during the summer months
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 a suspect or confirmed case of WNV, contact 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

Wear long-sleeved shirts, long pants, socks and shoes when outdoors
Use a Health Canada-approved mosquito repellent containing DEET or Icaridin
Drain areas of standing or stagnant water regularly, including bird baths, old tires, pails, toys and wheelbarrows
Ensure all windows and doors in your home have screens that are in good condition

More Information