MEDICAL ADVISORY: Heightened Surveillance for West Nile Virus Infections

Issued by:  Gayane Hovhannisyan, MD, MPH, PhD, FRCPC, Associate Medical Officer of Health (Acting)

Background

• Niagara Region Public Health & Emergency Services (NRPH&ES) has received its first confirmation of West Nile Virus (WNV) in mosquito pools for 2019
• 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. WNV Fever (20-30%)

An acute flu-like illness develops in most symptomatic cases:

• Fever
• Headache
• Myalgia/body aches
• Fatigue

• Nausea/vomiting

• Diarrhea
• Swollen lymph nodes
• Maculopaopular rash

3. WNV neurological syndrome (<1%), presenting as meningitis, encephalitis or acute flaccid paralysis.

Please consider WNV infection in patients presenting with one or more symptoms who have had mosquito bites within the preceding 14 days. The incubation period may be longer in immunocompromised individuals.

Testing

Acute and convalescent (2 to 3 weeks later) serology is the preferred test for WNV infection.

Please use the Public Health Ontario General Test Requisition Form and enter “Suspect West Nile Virus” under “Test Description.”

For additional information on the test and interpretation of the results:

Reporting

Please report all confirmed and suspected cases of WNV infection using the online Human Surveillance Patient Report Form.

For further information, please contact NRPH&ES, Infectious Disease program at 1-888-505-6074 or 905-688-8248 ext. 7330 Monday to Friday 08:30 am to 4:30 pm, after hours 905-984-3690.