The first case this season of West Nile virus has surfaced in Boulder County, infecting a 65-year-old man from Longmont, Boulder County Public Health said Friday. 

The mosquito-borne disease can cause fever and headaches, and in some cases lead to encephalitis, a brain infection. To date, there have been five reported cases in Colorado this year, according to the Colorado Department of Public Health and Environment. 

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“This is the time of year when we see the most people become ill from West Nile virus infections,” Sandra Sonoda, a communicable disease nurse at BCPH, said in a news release. “We all need to continue to be diligent about protecting ourselves from mosquito bites, particularly between dawn and dusk.”

West Nile virus is transmitted to humans who are bit by an infected mosquito.

Symptoms of the potentially deadly virus appear typically between three and 14 days after transmission and can include fever, extreme fatigue, headache and body aches. Skin rashes and swollen lymph nodes can also occur. Any anyone with these symptoms should seek medical attention, according to the U.S. Centers for Disease Control and Prevention. 

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While anyone can contract the virus, people over the age of 50 or those with weakened immune systems are at a greater risk to develop neuroinvasive diseases such as encephalitis or meningitis. 

About 10% of severely infected people die from the illness and survivors of severe cases can have long-term nervous system problems, according to the CDC. 

So far this year, three of the state’s five cases have been classified as neuroinvasive, according to CDPHE. 

In the Centennial State, most cases of West Nile virus are diagnosed in August and September, but can be found as early as May or as late as December, according to BCPH. 

Health officials have established the “Four D’s” in an attempt to reduce cases: 

• Drain: Mosquitoes breed in water. Drain any standing water in your yard each week. Bird baths, clogged gutters and kiddies pools are common breeding sites.
• Dress: Wear lightweight, long-sleeved shirts and long pants while outdoors. Spray clothing with insect repellent since mosquitos bite through clothing.
• Defends: Apply insect repellent sparingly to exposed skin. Use an approved repellent according to its label. During the peak season, infected mosquitoes can be found all along the Front Range, so use repellent where you live, work and recreate.
• Dawn/dusk: The best way to avoid West Nile virus is to prevent mosquito bites. Stay indoors, if possible during peak mosquito hours — sunset to 1.5 hours after sunset appear to be the most active “feeding time” for the species that carry West Nile virus.

For additional information about West Nile virus, click here. 

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