First Human Cases of West Nile Virus Reported in Colorado’s Adams County

The first two human cases of West Nile Virus (WNV) in Colorado this year have been confirmed by the Adams County Health Department, health officials announced Thursday.

The individuals likely contracted the virus in late June through mosquito bites, although no infected mosquitoes have been found in Adams County so far. Nearby counties, however—Weld, Boulder, and Longmont—have all reported positive mosquito samples, raising concerns across the region.

“The virus is transmitted through mosquito bites,” said Dr. Kelly Weidenbach, Executive Director of the health department. “To protect against it, we suggest using insect repellents, wearing protective clothing, or staying indoors during peak mosquito activity.”

West Nile Season Is Underway

West Nile virus season in Colorado typically begins in mid-July and peaks a month later. However, cases have been detected as early as May and as late as December, according to the Colorado Department of Public Health and Environment (CDPHE). The season usually ends with the first freeze.

Symptoms to Watch For

Most infected people do not show symptoms
Around 20% may experience flu-like symptoms
Less than 1% may develop serious health complications

How to Protect Yourself and Your Family

Health officials urge the public to take preventive measures seriously as mosquito activity increases:

Avoid Peak Mosquito Hours

Mosquitoes are most active at dawn and dusk
Try to stay indoors during these times if possible

Prevent Breeding Near Your Home

Eliminate standing water weekly from:
- Buckets, birdbaths, flowerpots, tires, toys, planters, trash cans
- Wheelbarrows, pools, and any other water-holding container
Check both indoor and outdoor areas for stagnant water
Avoid watering pavement or streets, which can create pooling
Minimize irrigation overspray to reduce puddles near gutters

Mosquito-Proof Your Home

Install or repair window and door screens

Wear Protective Clothing

Opt for long sleeves, pants, and socks when outdoors in mosquito-prone areas

Use EPA-Approved Repellents

Choose products containing:
- DEET
- Picaridin
- Oil of lemon eucalyptus
- Para-menthane-diol
Visit the EPA’s online database to find a repellent that suits your needs

As the season continues, Adams County health officials remind residents to stay vigilant and proactive to reduce mosquito exposure and prevent the spread of West Nile virus.

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