West Nile virus is a concern in Colorado, so what should you keep in mind?

September 21, 2022
A person being bit by a mosquito.

As summer turns to fall, West Nile virus is more active in Colorado. The seasonal pattern is nothing new, but health experts are concerned that serious cases and deaths began earlier than is typical.

A health advisory was issued on Aug. 31 by the Colorado Department of Public Health & Environment (CDPHE) after three deaths were reported due neuroinvasive cases of West Nile.

“We’ve seen more cases this year early on than in prior years, and so far, the mortality rate for people with neuroinvasive disease [as a result of West Nile] is higher than prior years,” said Dr. Kathryn Springer, an infectious disease physician who works with Centura-Porter Adventist Hospital.

“This may even out as the season goes on, and once temperatures fall below freezing a couple of nights in a row, mosquitoes get killed off and that’s when [the virus] dies down.”

Most people who contract West Nile won’t even know they’re infected, and a small percentage will develop mild illness like fever or headache. However, an even smaller number will develop serious illness.

Neuroinvasive disease is a severe form of West Nile that involves the brain and nervous system. It can include symptoms like confusion or seizures, and sometimes patients are left in a coma or develop paralysis. About five percent of people with this disease will die.

“There is no treatment for this, and it can take months or even years to recover, if a patient recovers at all,” Dr. Springer said. “If a person shows any mental status changes or nervous system symptoms, they should seek care, but most people have a very mild illness.”

Senior adults and people with suppressed immune systems are more at risk of severe disease and neuroinvasive disease.

“I usually say if you have a fever or worsening illness over five days, that should cause concern and you should seek evaluation, or if your fever is higher than 102.”

Dr. Springer said the most important thing is to prevent mosquito bites.

“Our mosquito population seems to be increasing in Colorado, partly because of suburban sprawl, climate change, and even migration patterns of birds contribute.”

She said it is important to make note of that when you’re outside by wearing protective clothing that covers your arms and legs and using mosquito repellants. You can also pre-treat your clothes with a repellent called permethrin.

Dr. Springer also advises to try to avoid being outside at dawn and dusk and avoid having open windows and doors in your home without screens.

“Avoid standing water around your home. Mosquitoes only need a little bit of water to breed.”

West Nile was first noticed in the U.S. in the late 1990s in New York and is now present in all states.

“A lot of people just don’t realize how serious West Nile can be because it is still relatively new to us in the United States. We don’t have a vaccine or treatment for West Nile, but there are researchers looking into vaccines.”