Quebec may see record-breaking number of West Nile virus infections in 2018

Infectious disease specialist Dr. François Milord says the mosquito-borne virus, which has killed four Quebecers this year, may have infected as many as 150. We'll know once the final numbers are tallied in November.

The mosquito-borne virus has killed 4 Quebecers this year but may have infected 150, specialist says

Nathalie and Josée Bellemare lost their sister, Sylvie, in September. She was the fourth Quebecer to die as a result of contracting the West Nile virus in 2018. (Radio-Canada)

Sylvie Bellemare died last month after being bitten by a mosquito in Sainte-Julie on Montreal's South Shore.

She was in good shape on a Monday, but by that Friday she was in intensive care — ultimately becoming one of four people confirmed to have lost their lives to the West Nile virus in Quebec this year.

"In less than 24 hours, she was in a coma, and then the diagnosis was encephalitis," recalls her sister, Nathalie Bellemare, who wants people to be better informed about the virus and its risks.

Another sister, Josée Bellemare, said her hope faded for Sylvie once she learned it was West Nile.

"It's hard to have doctors who are helpless. They would like to help us, but there is nothing to do," she told Radio-Canada. "Vaccines: there are none. Remedies: there are none."

Highest infection rate since 2012

Now, with the cold having chased away the last of the mosquitoes, Quebec public health authorities are tallying up the final number of confirmed West Nile infections across the province. It appears 2018 will be a record-breaking year.

"We have noticed an increase in the number of cases," said Dr. François Milord, an infectious disease specialist at Université de Sherbrooke and consulting physician for the Montérégie's public health department.

"It will probably be the year with the highest number of cases."

Across Quebec, 51 patients are confirmed to have contracted West Nile in 2018, and there are 45 probable infections, meaning doctors have diagnosed West Nile and testing will probably confirm that diagnosis, Milord said.

Dr. François Milord says four people are known to have died from the West Nile virus so far this year in Quebec, but the final tally will only be known once all test results are compiled in November. (Radio-Canada)

The final tally of confirmed cases should be ready by November, and Milord predicts that number will reach 150. The number of deaths, he said, could also increase once test results come back.

"We're still receiving results for cases at the moment. So the number is changing."

Previously, the worst year for West Nile infections was 2012, with 134 confirmed cases and five deaths. This year, Milord says, it will likely be worse.

Montérégie worst region hit

Sylvie Bellemare was infected by a mosquito in the Montérégie region — the region most affected by the virus this year with 12 confirmed cases and 38 probable cases so far.

There were 40 cases in Montérégie in 2012. Milord is projecting the final tally will find 60 to 65 this year.

The hot summer likely contributed to the increase in the mosquito population, he said, because warm temperatures do favour faster mosquito breeding.

Still, he noted, the spread of the disease remains poorly understood. 

"We think it is based on the cycle of the virus in nature," Milord said.

"There are other factors at play related to the cycle of the virus in the environment among birds, among others, and we do not control all these elements."

Few people experience symptoms

While the numbers may be up after a hot summer, most people show little to no symptoms. The virus rarely causes death and most people recover without treatment, says Santé Montréal.

One in five people who have the virus will experience minor symptoms such as fever or a mild headache. People over 50 and those with chronic diseases remain the most vulnerable to the infection.

According to Montreal's public health authority, July is when mosquitoes are more likely to be infected with the virus. (James Gathany/Centers for Disease Control and Prevention/Associated Press)

One in 150 infected patients — less than one per cent — will develop more serious complications such as meningitis (swelling of the brain lining) or encephalitis (brain swelling).

Milord agrees it is important that people stay informed about the virus because prevention is up to every individual.

Prevention the only protection

According to Montreal's public health authority, July is when mosquitoes are most likely to carry the virus.

The agency's website recommends people protect themselves with insect repellent. If outdoors, wear light-coloured, long-sleeved tops and long pants.

It is also recommended that people take measures to reduce the number of mosquito breeding sites by, for example, eliminating accumulated water in outdoor objects, keeping covers on garbage and properly maintaining swimming pools.

The Public Health Agency of Canada reported 215 clinical cases of West Nile virus across Canada by late September and, of some 16,000 mosquito pools tested, 553 mosquitoes tested positive for the virus.

The number of clinical cases in Canada has varied considerably since 2002. More recently, there were 21 cases in 2014, 80 in 2015, 104 in 2016 and 200 in 2017.

With files from Lauren McCallum and Radio-Canada


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