A West Nile Virus 鈥渆pidemic鈥� with as many as 500 human cases is expected to strike Ontario this summer, according to new research from Brock University.
The province and 36 municipal health authorities have been monitoring the virus in mosquito populations since it first arrived in Canada in 2001. Insects are trapped, sorted by species, and tested for West Nile every week from May through October.
The Brock University team used 12 years of this research, and combined it with data on human cases to predict the next wave of infections.
鈥淲hat our model is suggesting, given the very high number of positive mosquito pools we鈥檝e recorded thus far, is that we are ramping up to potentially a third epidemic,鈥� Brock University PhD candidate Bryan Giordano told 麻豆影视 Channel.
More than 250 鈥減ools鈥� of mosquitos have tested positive for the virus so far this season, Giordano explained.
鈥淲hen we throw that number into our prediction model, this comes up with approximately 500 human cases that we could have by the end of the season,鈥� he said.
The 2002 outbreak saw about 300 human cases, and the second epidemic year in 2012 saw about 250, according to Giordano. He expects the actual number of human infection this year will fall somewhere in between.
The findings are especially troubling for the south of the province, including Toronto, Hamilton, Halton Region, Peel Region, Windsor-Essex County, and York Region, where the majority of West Nile cases have occurred in the past. Halton recorded the largest number of human infections in 2002.
Giordano said it is still too soon to precisely predict when human West Nile infections will start to peak. Human infections lag behind the peak for mosquitos. Those numbers are still rising.
鈥淭his really depends on what are numbers are going to be like next week. If our positive mosquito pools are still ramping up, so we still haven鈥檛 hit that peak yet, then we are unable right now to estimate when the peak number of human cases will occur.鈥�
West Nile Virus was originally identified in 1937 from the blood of a woman living in the West Nile district of Uganda. Since its arrival in Canada there have been over 5,000 confirmed human cases. The Public Health Agency of Canada estimates that an additional 18,000 to 27,000 human cases may have occurred and gone unreported, since most West Nile cases are asymptomatic.
estimates 80 per cent of people bitten by an infected mosquito will not show any symptoms. The rest will experience fever, head and body ache, nausea, vomiting, and rashes on the back, chest, and stomach.
About one in 150 will have more serious symptoms such as muscle weakness, stiff neck, confusion, tremors, numbness, and sensitivity to light.
The late summer is the most important time to take precautions. That鈥檚 when mosquitos switch from feasting on birds to searching for other food sources, like humans.
How to protect yourself from West Nile
- Try to cover yourself up if you are outside between dusk and dawn when most mosquitos feed. Wear light-coloured clothing, and tuck your pant legs into your socks if possible.
- Eliminating standing water around your home reduces places for mosquitos to lay eggs. You can also cut down on places for the insects to hide by trimming overgrown bushes and shrubs.
- Bug repellants containing DEET are also effective.
