West Nile Virus

What is West Nile Virus?

West Nile virus (WNV) is a disease that mosquitoes spread to humans. It first appeared in the U.S. in 1999 in New York and has since traveled westward across the U.S., appearing in Colorado each summer.

All age groups are at risk for WNV. Although less than 1% of infected people develop severe illness, WNV can be serious or fatal to anyone, regardless of age or health. People over age 50 and those with compromised immune systems have the highest risk of severe disease.

West Nile Symptoms and Risks

Symptoms generally appear 3 to 14 days after exposure. Most infections are mild and symptoms include:

• fever
• headache
• body aches
• skin rashes (occasionally)
• swollen lymph nodes (occasionally)

More severe infections may include:

• headache
• high fever
• neck stiffness
• stupor
• disorientation
• coma
• tremors
• muscle weakness
• convulsions

People with these symptoms need to seek medical attention immediately.

West Nile virus can cause encephalitis (swelling of the brain) and/or meningitis (swelling of the brain's lining).

Information on this page is adapted from the Centers for Disease Control and Prevention, the Colorado Department of Public Health & Environment, and the Larimer County Department of Health & Environment.

This information is provided for general educational purposes and should not be interpreted as medial advice. Individuals should contact a qualified healthcare provider for diagnosis or treatment of any symptoms described.

How West Nile Virus Spreads

Infected birds carry the virus long distances. Mosquitoes then spread it locally by biting these birds. The mosquitoes can then pass the virus to humans and animals, primarily birds and horses. There is a vaccine for horses, but none for humans. House pets do not spread the illness.

Health departments across the state closely monitor human and horse illnesses and track the virus by testing dead birds and trapping mosquitoes.

When is mosquito season in Fort Collins?

Mosquito season in Colorado starts in the spring and ends in mid-September. Peak season for WNV-positive mosquitoes tends to be mid-July through early September, though WNV could be detected in mosquitoes earlier or later depending on that year's specific conditions.

Prevention and Protection

Protect Yourself with the Four Ds!

• Drain: Mosquitoes breed in water! Drain any standing water in your yard each week. Bird baths, clogged gutters and kiddie pools are common breeding sites.
• Dress: Wear lightweight, long-sleeved shirts and long pants while outdoors. Spray clothing with insect repellent since mosquitoes may bite through clothing.
• Defend: Apply insect repellent sparingly to exposed skin. Use an approved repellent according to its label.
• Dawn/Dusk: Limit time spent outdoors at dusk through dawn, when mosquitoes are most active and feeding.

Report and Request Services

Report Possible Breeding Sites

Community members can report potential mosquito breeding areas to Vector Disease Control International (VDCI) by calling 970-278-9977.

Request a Free Backyard Inspection

To help reduce the number of man-made larval mosquito habitats, the City offers free backyard inspections to local residents. At your request, a technician from Vector Disease Control International (VDCI), the City's mosquito contractor, will visit your home, review ways to reduce mosquito habitats, identify potential breeding grounds and treat potential larval sites with mosquito larvicides.

To request an inspection or report a property with standing water, call VDCI at 970-278-9977 or email your request (include your home address) to wschlatmann@vdci.net.

West Nile Virus Program

Program Policy & Management

The City of Fort Collins has contracted with Vector Disease Control International (VDCI) for mosquito monitoring and mitigation, with a focus on three primary areas:

• Education: The City provides information to the general public and to City employees about personal protection and source reduction measures.
• Data Gathering: To effectively combat West Nile virus, VDCI conducts a mosquito surveillance program that includes mapping potential mosquito breeding sites and uses light traps to monitor adult mosquito activity throughout the season.
• Mitigation: VDCI applies larvicide to breeding sites within a one-mile radius of Fort Collins city limits. The larvicide is a natural, non-toxic biological product that affects only mosquitoes and is not harmful to fish and animals. Residents can report potential mosquito breeding areas by calling 970-278-9977. If levels reach the predetermined policy threshold, the City and VDCI will partner on targeted adult mosquito spraying.

City monitoring and control efforts reduce — but cannot entirely eliminate — the risk of West Nile virus transmission.

West Nile Virus Technical Advisory Committee

The West Nile Virus Technical Advisory Committee meets to discuss the previous mosquito season and considers recommendations for future response guidelines. The committee is composed of City-appointed experts who provide technical expertise and make recommendations to City Council regarding the City's West Nile Virus Management Policy.