Public Health Alert – Powassan virus detected in ticks
Situation
As part of our fall active tick surveillance, Powassan virus was detected in 6 black-legged ticks (Ixodes scapularis) collected in the Fort Frances area. A cluster of 6 positive ticks in the same area indicates conditions for the virus to live and spread among tick populations may be occurring.
Northwestern Health Unit (NWHU) performs active tick surveillance (tick dragging) in the spring and fall to track the migration of tick populations throughout our region and identify tick-borne diseases they may carry.
Patients are infected with Powassan virus following a bite from an infected black-legged tick. The virus may be transmitted from the tick in as little as 15 minutes of attachment, which is significantly less time than other tick-borne diseases such as Lyme disease and Anaplasmosis.
Most Powassan virus infections are asymptomatic. Symptoms of Powassan virus infection can develop from 1 to 4 weeks following a tick bite. Individuals may develop an initial prodrome of fever, chills, headache, gastrointestinal symptoms, myalgias, confusion, weakness, or nuchal rigidity, among other symptoms. Neuroinvasive disease may present as meningitis and/or encephalitis accompanied by neurological deterioration or other focal neurologic signs/symptoms. Testing should not be performed on asymptomatic individuals. (Clinical Presentation, Appendix 1: Case Definitions and Disease Specific Information, Ministry of Health)
Actions requested
- Consider Powassan virus disease as a possible diagnosis when seeing patients.
- Follow current testing guidance Test Information Index | Public Health Ontario
Reporting
- Powassan virus disease was added as a Disease of Public Health Significance (DoPHS) in Ontario on July 1, 2023.
- Notify NWHU when you suspect or confirm any Disease of Public Health Significance
Need more information?
- Disease and condition information for health care professionals, Northwestern Health Unit
- Tick-borne disease and tick surveillance, Northwestern Health Unit
- Powassan Virus, Public Health Ontario
- Appendix 1: Powassan Virus Infection Case Definitions and Disease-Specific Information, Ministry of Health
- Disease Brief: Powassan Virus, National Collaborating Centre for Infectious Diseases
- Powassan Virus, Public Health Agency of Canada
- Powassan Virus, Centres for Disease Control and Prevention
Contact:
Dr. Kit Young Hoon
Medical Officer of Health
Northwestern Health Unit