West Nile virus is being detected earlier this summer that it has in the past, and the province's chief medical officer is urging Ontarians to protect themselves.

The first detected case in Hamilton was found June 25 in a mosquito trap in Dundas, the city's public health department said in a release. That's the earliest in the summer season the mosquito-carried virus has been detected in Hamilton. The previous earliest detection was July 17, in 2012.

A few days after the Dundas case, West Nile was also detected in a mosquito in Durham region. So far this year, there have been no human cases. Last  year, Hamilton had 20 human cases.

"The vast majority of our West Nile cases are identified in August and September," said Dr. Arlene King, Ontario's chief medical officer. "That being said, it's not unheard of and people need to start thinking right now about protecting themselves."

King said our recent weather patterns - lots of rain and very hot and humid - can encourage growth in mosquito populations.

"Certainly a combination of warm weather and wet weather is more likely to enable the proliferation of mosquitoes so we need to remain vigilant," she said.

As for testing, the public health department sets up about 30 traps around the city on a weekly basis, said Richard MacDonald, a spokesperson for public health.

The traps run overnight and have a block of dry ice in them that emit carbon dioxide to mimic human breath and a black light. Mosquitoes are first attracted to the carbon dioxide, then the dark light brings them in further. The mosquitoes are blown down into a net by a fan.

When it comes to protection, MacDonald recommends residents dump any standing water, avoid areas with a heavy mosquito presence and wear light clothing.

"Mosquitoes are attracted to darker colours and more intense colours, so whites and light blues are better," he said.