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June 29, 2023

Mosquitoes in Boulder County Tests Positive for West Nile Virus

Boulder County, Colo. – Boulder County Public Health (BCPH) has confirmed that mosquitoes in a mosquito pool have tested positive for West Nile virus (WNV). The positive pool came from a trap located near Erie.

“Unfortunately, wet weather followed by high temperatures creates an ideal environment for mosquitos to breed,” said Lane Drager, Boulder County Public Health Consumer Protection Program Coordinator. “Over the holiday weekend and throughout the summer, take time to protect yourself, your family and your community from West Nile virus.”

WNV is transmitted to humans from the bite of an infected mosquito. While most infections are mild, the more serious infections can cause encephalitis (inflammation of the brain) and/or meningitis (inflammation of the brain’s lining), loss of vision, paralysis, coma, tremors, convulsions and death.

Symptoms of WNV include fever, extreme fatigue, headache, body aches and occasionally skin rashes and swollen lymph nodes. Generally, symptoms appear three to 14 days after being bitten by an infected mosquito. Anyone who experiences these symptoms should consult their health care providers.

There is no treatment, cure, or human vaccination for the virus. Health care providers can only treat the symptoms to help patients feel better and recover quickly.

BCPH officials urge residents to take precautions to protect themselves. Keep safe this summer, and remember the 4Ds:

  1. Use DEET-enhanced insect repellent or alternative.
  2. DRESS in long sleeves and pants.
  3. Avoid the outdoors from DUSK until DAWN.
  4. DRAIN standing water outside your home.

Generally, the mosquito season extends from late April until mid-October, with the end usually signaled by the first freeze in the fall.

Visit for more information about West Nile virus, mosquito activity in Boulder County and steps you can take to protect yourself and your loved ones this summer.