The first two human cases of West Nile virus in Colorado in 2018 have been reported in Weld and Delta counties. The Colorado Department of Public Health and Environment reminds people that preventing mosquito bites is the No. 1 way to avoid getting any mosquito-borne illness.

Weekly mosquito testing for West Nile virus began statewide in June. Adult mosquitoes are trapped and tested to provide an estimate of the number that are infected. The results help pinpoint the risk to humans in the area. West Nile virus-positive mosquitoes have been found in Adams, Boulder, Larimer and Weld counties this season. Not all counties and municipalities test mosquitoes, so it’s important for all Coloradans to take steps to protect themselves throughout the summer. 

“When the virus is present, people are at risk,” said Jennifer House, state public health veterinarian. “Use an effective insect repellent, wear protective clothing or stay indoors when mosquitoes are active, and mosquito-proof your home.” Most human West Nile virus cases are reported in August and September.

 In 2017, there were 68 human cases of West Nile virus in Colorado, including four deaths.

 Most people who are infected with West Nile virus don’t have symptoms. About 20 percent have flu-like symptoms, and fewer than 1 percent develop a serious, potentially deadly illness, such as the one reported in Weld County last week. 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 often. Empty water from tires, cans, flowerpots, clogged gutters, rain barrels, birdbaths, toys and puddles.
• Install or repair screens on windows and doors.