Mosquito-Spread West Nile Virus Persistent Wyoming Threat


West Nile virus remains a persistent, potentially serious threat for state residents during the summer months, according to the Wyoming Department of Health.

Katie Bryan, a WDH epidemiologist, said mosquitos spread West Nile virus when they feed on infected birds and then bite people, animals and other birds.

“Most people infected with West Nile virus do not realize it’s happened,” Bryan said. Among those who become ill, symptoms include fever, headache, body aches, skin rash and swollen lymph nodes. A very small percentage of those infected develop West Nile neuroinvasive disease with symptoms such as severe headache, fever, neck stiffness, stupor, disorientation, coma, tremors, convulsions and paralysis.

Since WNV first appeared in Wyoming in 2002, reported human cases each year have ranged from two with no deaths in one year to 393 and nine deaths in another. In 2016, 10 WNV cases were reported to WDH. Of the reported cases, seven involved people with neuroinvasive disease.

“Overall, West Nile virus could be underreported,” Bryan said. “We’ve learned testing and reporting is more likely when people are seriously ill.”

“Avoiding mosquito bites is key with West Nile virus, and there are active steps we should all take,” Bryan said. The “5 D’s” of WNV prevention include:

1) DAWN and 2) DUSK – Mosquitos that spread WNV prefer to feed at dawn or dusk, so avoid spending time outside during these times. 3) DRESS – Wear shoes, socks, long pants and a long-sleeved shirt outdoors. Clothing should be light-colored and made of tightly woven materials. 4) DRAIN – Mosquitos breed in shallow, stagnant water. Reduce the amount of standing water by draining and/or removing. 5) DEET – Use an insect repellent containing DEET (N, N-diethyl-m-toluamide). When using DEET, be sure to read and follow label instructions. Other insect repellents such as Picaridin (KBR 3023) or oil of lemon eucalyptus can also be effective.

More information about WNV in Wyoming is available online at

Zika virus, another mosquito-related disease, is spread to people mostly through bites of certain types of infected mosquitos that do not live in Wyoming. Pregnant women and women trying to become pregnant, as well as their partners, should pay attention to Zika-related travel warnings. More information about Zika virus can be found online at