The Colorado Department of Public Health said mosquitoes testing positive for the West Nile virus have been found in Delta, Mesa, Adams, Boulder and Weld counties.
Veronica Daehn Harvey, a spokeswoman for the Mesa County Health Department, said last year the county had 11 human cases of the virus and one death.
Harvey said it’s important for people to protect themselves from mosquito bites so they don’t contract the virus.
She said people should wear an insect repellent either with DEET or with use a natural alternative such as picaridin or oil of lemon eucalyptus.
"Dress in long sleeves when you are in areas where mosquitoes are active," she advised. "[Also] if you have any standing water on your property you’ll want to drain that because mosquitoes do like to breed in pools of standing water. And stay indoors at dusk and dawn if you can because that’s the time of day when mosquitoes are most active.”
The state department of health said there have been no human cases of West Nile reported so far this year.