DDPHE Confirms First 2026 Human Case of West Nile Virus in Denver

DDPHE Confirms First 2026 Human Case of West Nile Virus in Denver

Published on September 21, 2026

As the first day of fall arrives tomorrow, the Denver Department of Public Health & Environment (DDPHE) is reminding residents that mosquitoes are still active and the risk of West Nile virus continues into the fall. DDPHE recently confirmed Denver's first human case of West Nile virus for 2026 and urges residents to continue taking steps to prevent mosquito bites.

West Nile virus is most commonly spread through the bite of an infected mosquito and has been regularly reported in Colorado for more than 20 years. While mosquito activity begins to decline as temperatures cool, mosquitoes remain active into the fall. In Denver, the risk of West Nile virus continues until the first frost, which typically occurs in October.

DDPHE's mosquito control program continues seasonal monitoring and treatment across Denver to help reduce larval mosquito populations and the risk of West Nile virus to the public. Residents can also take simple steps to protect themselves from mosquito bites and reduce mosquito habitats and breeding around their homes.

DDPHE recommends the following precautions:

• Use insect repellents containing DEET or picaridin when spending time outdoors. These repellents are safe and effective when used as directed, including for pregnant and breastfeeding individuals.
• Limit outdoor activities during dusk and dawn, when mosquitoes are most active.
• Wear loose-fitting, long-sleeved shirts, long pants and tall socks when outdoors.
• Drain standing water around your property, including water collected in flower pots, bird baths, toys, buckets and other containers.
• Maintain fountains and swimming pools to ensure proper water circulation or drain and cover them when they are not in use.
• Install or repair screens on windows and doors to keep mosquitoes outside.
• Avoid watering on paved areas, which can create puddles where mosquitoes can breed.

There is no specific treatment for West Nile virus, making prevention especially important. About one in five people infected with West Nile virus may develop symptoms such as fever, headache, body aches, joint pain, rash or gastrointestinal symptoms. Older adults and people with weakened immune systems, including people taking certain medications that suppress their immune system, are at greater risk for severe illness.

Residents experiencing symptoms, particularly severe headache, confusion or worsening symptoms, should contact a health care provider.

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