An 80-year-old man has been hospitalized and a 32-year-old woman is recovering from probable West Nile virus, in what could be the first cases of the disease detected in Toronto this year.

Toronto Public Heath announced the cases Thursday.

The announcement came one day after Toronto associate medical officer of health Dr. Howard Shapiro told reporters that the city had found a higher-than-usual number of mosquitoes testing positive for West Nile virus, which is transmitted the insects.

He said Thursday that a mild winter and hot weather were likely to blame for the high numbers of infected mosquitoes, as the West Nile virus multiplies faster in warm temperatures.

Shapiro said he was not able to give any additional information on the affected patients due to confidentiality.

He said that Toronto Public Health should be able to confirm the West Nile cases when additional lab results come back, likely near the end of next week.

Officials believe both patients potentially contracted the virus in Toronto.

“We definitely do check travel histories of people and there is nothing that leads us to believe that they contracted it somewhere else, at this point,” Shapiro said.

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

Those infected experience fever, headache, rash and fatigue.

Symptoms can last a week or more, Shapiro said.