A warm, wet summer has created the ideal breeding ground for mosquitoes.
Chuck Rodosevich of Colorado Mosquito Control says this summer is one of the worst he's ever seen in Pueblo County.
"This is an unusual summer and it's been much worse for mosquitoes for two major reasons," he said.
Rodosevich says recent rain combined with a high-flowing Arkansas River made for the perfect storm.
"The Arkansas was running very high early in the season and it flooded a lot of low lands."
Colorado Mosquito Control test about 300 sites weekly in Pueblo County for mosquito larvae. "You take an area, like this, untreated, it can produce literally millions of mosquitoes," Rodosevich said, while pointing to a pond near Runyon Lake. "Once they've hatched and spread, they can go for miles."
Earlier this month, a pool of mosquitoes in Pueblo County tested positive for West Nile Virus. A middle-aged man in Pueblo County also tested positive for the virus.
"As soon as you start to see West Nile pop up, your anxiety really gets heightened," Rodosevich said.