Mosquitoes carrying West Nile virus have been found in three Colorado counties. No human cases have been reported, but everyone is advised to take precautions.

The Colorado Department of Public Health and Environment says the mosquito samples that tested positive were gathered in Delta, Larimer and Weld counties. The virus is carried by certain infected birds and transmitted to people by bites from female Culex mosquitoes that have fed on infected birds.

Studies show that cool, wet weather in early spring followed by very hot temperatures throughout the summer could result in more mosquito activity.

Health officials suggest these “five Ds” as precautions against the West Nile virus.

-DRAIN standing water in your yard weekly, since that’s where mosquitoes lay eggs. Drain tires, cans, flower pots, clogged rain gutters, rain barrels, toys and puddles.

-DUSK and DAWN are when mosquitoes that carry the virus are most active, so limit outdoor activities or take precautions to prevent mosquito bites.

-DEET is an effective ingredient to look for in insect repellents. Always follow label instructions carefully.

-DRESS in long sleeves and pants during dawn and dusk or when in areas where mosquitoes are active.