OKLAHOMA CITY (AP) — Oklahoma has had 170 confirmed cases of West Nile disease and 11 deaths, the state Department of Health said Tuesday in its bi-weekly report.

While the number of reported deaths rose from nine the previous week, health officials said the spread of the disease had slowed as cooler weather limited the activity of the Culex mosquito, which spreads the virus to humans through its bite.

“The number of West Nile Virus reports that we’re receiving has consistently declined since the middle of September,” said Dr. Lauri Smithee, chief of acute disease service at the Health Department.

The state also benefitted by earlier-than-usual freezing temperatures, which drive the mosquito into dormancy. The first freezing temperatures of the season were recorded during the first week of October at various stations around the state, according to the National Weather Service. That was two to three weeks before the average first freeze.

“Mosquitoes are slowing down,” Smithee said. “Indeed, there is less transmissions going on.”

The latest deaths involve people who contracted the disease earlier, when its spread was more prevalent, she said.

Among the victims this year are former Guthrie Mayor Jon Gumerson, who died Oct. 6

Oklahoma County has the most confirmed cases with 54 and has had two deaths. Tulsa County is second in total cases with 32 and has had the most deaths with 3. Two deaths were reported in Carter County and one each in Seminole, Muskogee, Cleveland and Logan counties.

Despite the cooler weather, Smithee said residents should stay vigilant, use an insect repellant containing DEET and limit their time outdoors during mosquitoes’ most active time.

“I think we should continue to caution individuals, especially if they’re out in the early morning, in the dawn hours,” she said. “We certainly still have the virus circulating, the risk is still there.”

Smithee said those most at risk continue to be adults over age 50 because of their weaker immune systems