The city of Longmont wants to spray for mosquitoes ahead of a popular festival, after finding hundreds of mosquitoes in a trap last weekend.

The 22nd annunal Rhythm on the River will take place at the Roger's Grove Nature Area on Friday and Saturday.

Last weekend, crews trapped nearly 270 mosquitoes at Roger's Grove, which is more than double what they typically trap. 72 mosquitoes (nearly 30% of the mosquitoes in the trap) have the potential of carrying the West Nile Virus, according to Mike "Doc" Weissmann, the Chief Entomologist with Vector Disease Control International.

The group was contracted by the city of Longmont to test mosquitoes and help mitigate the potential for bites. The number of mosquitoes found at Roger's Grove are double what's required to begin spraying, according to Weissman.

"We want to test the mosquitoes because they're kind of like the canary in the coal mine," he said. "Mosquitoes start getting positive before people do."

Colorado has had at least one positive case of West Nile every year since 2003, when the disease was introduced to our state.

So far this season, a human case of West Nile was reported in Jefferson County, along with an infected mosquito pool in Larimer County. That's on track for Colorado, according to Weissmann.

While the virus can be scary, he wants people to know the truth about the disease.

"Most people who get the disease won't even show symptoms," Weissmann said "It's only one out of 150 that even gets severe symptoms but it could happen to anyone."

Because the threat still exists, experts say people still need to be careful.

"People do have to be aware that this time of year, there are infected mosquitoes out there that could transmit disease," he said.

Crews will begin spraying Roger's Grove at 9 p.m. Thursday night. The festival runs Friday and Saturday.

The city also asked crews to spray several neighborhoods in Longmont.