Toronto Public Health is warning residents to take precautions as the city sufferes the largest outbreak of West Nile Virus in the past decade.

Dr. David McKeown, Toronto’s Medical Officer of Health said 46 human cases of West Nile Virus have been reported so far this summer, with more cases likely to be discovered in the coming weeks.

“While most people infected with WNV will recover, the virus can have serious health impacts - especially for seniors and those with compromised immune systems. In rare cases it can be fatal,” McKeown said in a statement released Thursday.

“I urge everyone to take precautions to avoid being infected with the virus.”

West Nile virus affects about one in five people who are bitten by an infected mosquito.

Those infected experience fever, headache, rash and fatigue that can last a week or longer.

About one in 100 cases of West Nile virus can cause an infection in the central nervous system, usually in the brain, which can be fatal.

In 2002, Toronto Public Health had 163 reported cases, with the number dropping to 44 the following year.

The warning echoed numbers released by Public Health Ontario on Wednesday, which suggested the prevalence of West Nile Virus in southern Ontario is on track to equal its worst year ever. The provincial health group said 82 cases have been reported across the southern Ontario region, and the number is likely to match the 186 cases reported in 2002.

Toronto Public Health says it has placed 43 mosquito traps around the city in order to test mosquitoes on a weekly basis.

The city has also conducted four rounds of larviciding around Toronto in an attempt to reduce the mosquito population.

The public is urged to protect themselves from mosquito bites by using repellent, covering up and going indoors at dusk and dawn, when mosquitoes are most active.