COLORADO — The State Department of Public Health and Environment (CDPHE) has reported finding two human cases of West Nile virus (WNV) in Colorado for the first time this season. One case is from Larimer County and the other case is from Delta County. Both patients have survived and are now recovering from their illnesses. West Nile virus is most commonly spread to people by the bite of an infected mosquito. WNV-positive mosquitoes have been found in Adams, Boulder, Delta, Denver, Larimer, and Weld counties this year.  

“There are simple precautions people can take to protect themselves from West Nile virus,” said Dr. Jennifer House, deputy state epidemiologist and public health veterinarian. “Use an effective insect repellent, wear protective clothing, or stay indoors when mosquitoes are active, and mosquito-proof your home.” 

In Colorado, most human West Nile virus cases are reported in August and September.

In 2020, Colorado had 35 reported human cases of West Nile virus, including one death.

Most people infected with West Nile virus don’t have symptoms. About 20% of infected people will have flu-like symptoms, and fewer than 1% develop a serious, potentially deadly illness. People over age 60 and those with certain medical conditions are at greater risk of serious illness. See a health care provider if you develop severe headaches or confusion.

To protect yourself:

• Use insect repellents when you go outdoors. Repellents containing DEET, picaridin, IR3535, and some oil of lemon eucalyptus, and para-menthane-diol products provide the best protection. Follow label instructions.
• Limit outdoor activities at dusk and dawn, when mosquitoes that carry West Nile virus are most active.
• Wear protective clothing (long pants, long-sleeved shirts, and socks) in areas where mosquitoes are active. Spray clothes with insect repellent for extra protection.

To mosquito-proof your home:

• Drain standing water around your house at least once every week. Empty water from tires, cans, flowerpots, clogged gutters, rain barrels, birdbaths, toys, and puddles.
• Install or repair screens on windows and doors.