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Human case of West Nile Virus confirmed in Boulder County

This is the second human case of West Nile virus in the region this year, with a human case confirmed in Larimer County last week
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Stock photoPhoto by Jimmy Chan

NEWS RELEASE
BOULDER COUNTY PUBLIC HEALTH
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Boulder County Public Health (BCPH) has confirmed that a Lafayette resident has contracted the first human case of West Nile virus (WNV) in Boulder County in 2023. The resident, in their 40s, was believed to be infected while in Lafayette and has not been hospitalized. This is the second human case of West Nile virus in the region this year, with a human case confirmed in Larimer County last week.

Due to heavier rainfall and larger mosquito populations, the risk of contracting West Nile virus is more significant now than in previous years, and periods of high risk may increase in the future due to the effects of climate change. Residents are strongly encouraged to understand their risk and take steps to protect themselves, their families and friends from potentially dangerous mosquito bites.

“There has been a significant increase in mosquitoes in Boulder County this summer. The number of Culex species (the kind that transmits WNV to humans) captured in surveillance traps in recent weeks has been over five times greater than the average for this time of year,” said Alayna Younger, Boulder County Public Health Epidemiologist. “Residents need to take steps to stay healthy—drain standing water around your home, avoid activity outdoors around dusk and dawn and wear insect repellant and long sleeves and pants whenever you’re outdoors after dusk.”

West Nile virus symptoms typically include fever, extreme fatigue, headache and body aches but can also occasionally include skin rashes and swollen lymph nodes. Symptoms generally appear two to 14 days after being bitten by an infected mosquito. Eight out of 10 people infected with West Nile virus do not develop any symptoms.

West Nile virus 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.

While everyone is at risk of being infected with West Nile virus, those over 60 or with weakened immune systems are at greater risk of developing serious illness. Anyone who experiences these symptoms should consult their health care provider. There is no treatment, cure, or human vaccination for the virus, but health care providers can treat symptoms to help patients feel better and possibly recover more quickly.

Most Colorado cases of West Nile virus are diagnosed in August and September but can also be identified as early as May and as late as December. Generally, the mosquito season extends from late April until mid-October, with the end usually signaled by the first freeze in the fall.

Boulder County Public Health officials urge residents to learn about personal West Nile virus prevention 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. 

For more information about West Nile illness, mosquito activity in Boulder County or proactive steps to take, visit www.boco.org/WNV.

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