23 cases of West Nile virus so far this month in Montreal

A mosquito feeds at the Salt Lake City Mosquito Abatement District on July 26, 2023, in Salt Lake City. Mosquitoes can carry viruses including dengue, yellow fever, chikungunya and Zika. They are especially threatening to public health in Asia and Africa but are also closely monitored in the United States. (AP Photo/Rick Bowmer)

Montreal public health is noting an increase in West Nile virus infections in the city, leading to neurological damage in nearly a dozen local patients.

As of Tuesday, there were 25 cases of the virus reported this year among Montrealers, 23 of which occurred in September, according to a notice the health agency posted Wednesday.

That’s much higher than the historical average of 8.8 cases in September between 2010 and 2019. The highest number recorded for the month of September is 33 cases, in 2018.

The public health agency says an investigation is still ongoing for several recent cases, but that the people infected are believed to have been exposed on the island of Montreal.

Of the 25 reported cases, 21 are people over the age of 50, and at least 10 patients have experienced neurological damage.

• READ MORE: West Nile virus in Canada: What to know

The first confirmed case of West Nile virus in Quebec for the current season was reported on Aug. 21 in a Montreal resident.

West Nile virus is transmitted primarily through the bites of infected mosquitoes and has an incubation period ranging from two to 15 days.

Most cases occur between July and October, with a peak in August and September. Montreal public health said personal protective measures against mosquito bites remain the most effective way to prevent the virus and other similar infections.

People aged 50 and older and those with chronic diseases like diabetes, cancer and heart disease are at higher risk of serious infection, the agency said.

Montreal public health is advising the medical community to test any patients for West Nile virus if they have a fever and any of the following:

• A viral syndrome requiring hospital consultation, including headache, severe fatigue, myalgia, arthralgia, lymphadenopathy, and maculopapular rash
• A neurological syndrome such as encephalitis, viral meningitis, acute flaccid paralysis, abnormal movements, Parkinsonism or Parkinson-like syndrome, other neurological syndromes.

Medical professionals are required to report all cases of West Nile virus to their local public health department.