Larimer County Spraying to Kill West Nile Mosquitoes After Finding More Than Usual

Josh Cassidy/KQED

Larimer County is spraying to kill mosquitoes this week after tests found high numbers of insects infected with West Nile virus.

Traps in central and north Fort Collins caught significantly more mosquitoes with West Nile than in previous weeks, according to the Larimer County Department of Health and Environment. The department will spray pesticides in those areas Wednesday after 8 p.m. to cut down on the risk of infection. They already sprayed areas on Sunday.

The West Nile season usually starts with a slow uptick in infected mosquitoes in early August. This sharp increase in infected bugs in September is uncommon. The delay was due to hot weather, health officials said.

"We went from, 'Yes, we know it's here, and we've had positive pools' to 'Holy cow that risk has exceeded what we are comfortable with, and we need to spray' pretty quickly," said health department spokesperson Katie O'Donnell. "Normally we have most of the summer to get to that point."

There have been three reported human cases of the virus in Larimer County this year. The health department expects that number to rise in coming weeks as the incubation period can be as long as a month, meaning that's how long it can take for an infected person to show symptoms, O'Donnell said.

Statewide, there have been 14 cases. Positive pools of mosquitos have also been found in Weld, Boulder, Adams, La Plata, Pueblo, Delta and Mesa counties this year.

In Fort Collins, officials recommend people stay inside for 30 to 60 minutes after spraying to reduce their exposure to the chemicals. They also recommend bringing pets indoors and covering organic gardens with tarps.