Ontario may face a new West Nile virus epidemic

ST. CATHARINES Ontario is on the cusp of another West Nile virus epidemic, according to new research published by Brock University scientists.

In a new paper published in the open-access, peer-reviewed journal PLOS ONE, medical entomologist Fiona Hunter and her graduate student Bryan Giordano predict that based on the number of mosquitoes found in Ontario carrying the virus, about 340 people will be infected by early fall.

“I was very confident in 2012 before we had the West Nile outbreak that year,” Hunter said in an interview Tuesday, hours after the paper was published. “I am even more confident of the prediction this year because the data are so robust. (Giordano) has looked at all the data, backwards, forwards and upside down.”

Hunter said that Giordano, the lead author on the paper, used the past 15 years of Public Health Ontario data on West Nile virus infections to develop an equation that predicts the number of human cases based on the number of mosquitoes found carrying the virus.

So far this year, 250 pools of mosquitoes in the province have been found to carry West Nile virus.

Hunter said while Ontario has hit the peak of mosquito season, the model expects the total number of pools to reach 500 over the next six to eight weeks.

That translates into about 340 infected humans, which is about the same as the 2012 outbreak, which killed two people. The 2012 outbreak was the most significant since the 2002 West Nile virus epidemic that saw 394 people infected.

There are currently 16 reported human cases in Ontario. Earlier this month, Niagara had its first report human infection of 2017.

The virus is spread to humans by mosquitoes that have fed on infected birds.

Most people do not show symptoms, but about one in five infected people will suffer symptoms that may include headaches and fever, nausea, body aches and a rash.

One in 150 people will suffer a high fever, muscle weakness and a sudden sensitivity to light. In very rare cases, people can die from an infection. There is no cure or vaccine for West Nile virus, and experts recommend if you are going outside between dusk and dawn, which is when mosquitoes feed, you should wear long sleeves, light-coloured clothing and use insect repellent that contains DEET.

Hunter, who has become known internationally for her work on tracking the global spread of the Zika virus, said Ontarians need to take the situation seriously and start using insect repellent.

“What happens is that as the summer draws to an end, the birds the mosquitoes were feeding on are gone, the mosquitoes get way less choosy,” Hunter said.

While other species of mosquitoes that are more of a nuisance are dying off at this time of year, the culex species of mosquito that carries the virus sticks around for the next six to eight weeks.

“So just because you didn’t get bitten earlier in the summer, doesn’t mean you should think you cannot get bitten now,” Hunter said.