DENVER — Weekly mosquito testing for the West Nile virus began across Colorado this week.

The first human case of West Nile has already occurred this year. A Larimer County resident developed symptoms in late May and is recovering.

Colorado Mosquito Control has 200 trap sights around the state where it captures and tests mosquitoes.

“By monitoring these sights each year, we get an idea of the relative amount of West Nile from year to year,” Chief entomologist Doc Weissmann said.

It tests the number of mosquitoes, the species and if they carry the West Nile virus. Last year, 101 cases of West Nile were reported in Colorado, including three deaths.

“Most people just get light symptoms if anything at all, but those that do get bad symptoms could be hospitalized or even die,” Weissmann said.

Weissmann said there are about a half-dozen mosquito species in Colorado that can carry the virus, and those types of mosquitoes start to increase this time of year.

“It shouldn’t make people afraid to go outside. Jst take precaution,” he said. “If you can avoid being out during dusk and dawn, you want to avoid those times. If you do have to be out during those times, either wear long sleeves or loose clothing, or wear mosquito repellent, especially those that have DEET in them.”

There’s no real way to predict a mosquito season; it depends a lot on the weather conditions, but some areas are more prone to bites than others.

“Some of the counties like Weld, Larimer and Boulder County, we see cases every year,” Weissmann said. “Wherever you find flood water, irrigation you tend to see more (mosquitoes). And along rivers you tend to see more.”

Adult mosquitoes captured in traps are tested to obtain an estimate of how many infected mosquitoes might be flying around. Local public health officials then notify the public of the risks in certain areas.