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

Issued by:  Andrea Feller, MD MS FAAP FACPM, Associate Medical Officer of Health

Background

• Niagara Region Public Health & Emergency Services (NRPH&ES) has received its first confirmation of West Nile Virus (WNV) positive mosquito pools for 2020
• All health care providers are encouraged to be on heightened surveillance of WNV infection
• To date, NRPH&ES has not received a laboratory confirmed WNV human case

Clinical Presentation

1. Asymptomatic (70-80%). The majority of WNV infections are asymptomatic.
2. West Nile Fever (20-30%) is typically a mild illness lasting 3 – 6 days
3. Meningitis, encephalitis and/or acute flaccid paralysis develop in <1% of WNV infected individuals

Symptoms:

• Fever
• Headache
• Myalgia/body aches
• Fatigue
• Nausea/vomiting
• Diarrhea
• Swollen lymph nodes
• Maculopaopular rash

Please consider WNV infection in patients presenting with one or more symptoms. First symptoms usually appear within 2 – 15 days after infection.

Testing

• Refer to Public Health Ontario for specimen collection and handling information
• Please use the Public Health Ontario General Test Requisition Form and enter “Suspect West Nile Virus” under “Test Description”

Reporting

Please report all confirmed and suspected cases of WNV infection to our 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., after hours 905-984-3690.

Surveillance

The Public Health Ontario West Nile Virus Surveillance Tool summarizes Ontario mosquito, human and weather data. It is updated each Wednesday from July to October, with data provided by local public health units (mosquito and human data), as well as Environment Canada (weather data).