The Denver Department of Public Health & Environment (DDPHE) is urging residents to take extra precautions after disease intervention specialists confirmed the city’s first human case of West Nile virus this season.
West Nile virus is primarily spread through the bite of an infected mosquito and can be transmitted anytime when mosquitoes are active. In Colorado, mosquitoes can be active as early as May but are typically in higher numbers during summer through fall. Mosquito season ends after the first hard freeze of the year, usually in October or November.
The best way to prevent West Nile virus is to avoid being bitten by mosquitoes. Mosquitos need water to breed, so getting rid of standing water is key. Eliminate standing water where mosquitoes can breed. Once a week, empty and scrub, turn over, cover, or throw out items like tires, buckets, planters, toys, pools, birdbaths, and trash containers. Clean out street and house gutters that may hold water.
Additionally, DDPHE recommends the following preventive measures:
- Avoid watering cement or streets, which can create mosquito-friendly puddles.
- Use insect repellents, like DEET, which are safe and effective when used as directed, even for pregnant or breastfeeding individuals.
- Limit outdoor activity at dawn and dusk when mosquitoes are most active.
- Wear long sleeves and pants when outside.
- Ensure windows and doors have intact screens to keep mosquitoes out.
Common symptoms of West Nile virus disease include fever, fatigue, headaches, and body aches, with some people also experiencing rashes or swollen lymph nodes. Symptoms typically appear 3–14 days after being bitten. While anyone can be infected, those over 50 or with weakened immune systems are at higher risk for severe illness. Severe infections begin suddenly and can include symptoms of high fever and headache, neck stiffness, disorientation, and tremors. Severe infections may lead to a serious brain infection such as encephalitis or meningitis, paralysis, coma, or even death.
Residents experiencing symptoms should consult their healthcare provider immediately. Treatment can help ease symptoms and aid recovery.
For more information on West Nile virus in Colorado or local mosquito monitoring, visit CDPHE’s website. You can also learn how Denver manages its mosquito population on DDPHE’s Environmental “What If” Podcast.
