Pitkin County mosquitoes might carry West Nile Virus, says epidemiologist

The county’s public health department reported on Thursday that a long-term Pitkin County visitor contracted West Nile Virus, likely within the county. Officials identified the probable transmission in the week of Aug. 21.

“We’re assuming that exposure occurred within county borders. That being said, mosquitoes are ubiquitous, and they don’t care for county borders. It is entirely possible that they could have gotten a mosquito bite if they went down to Target (in Glenwood Springs),” said Carlin Senst, the county epidemiologist. “But because of (the patient’s) extended stay in Pitkin County and no recent travel events, it led us to assume the probable exposure was within the county itself.”

According to Senst, cases of West Nile Virus are on the rise statewide in both people and horses, which are particularly susceptible. If it were possible to definitively prove the patient contracted the disease within Pitkin County, it would be the first official, locally-transmitted case. 

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The state tracker records confirmed cases by county of residence, not by assumed county of exposure, Senst said. The case in Pitkin County is not reflected on the state map because of that. 

Previously, public health experts in the High Country considered their regions out of the habitat zone for the virus-carrying mosquitoes due to the altitude. But warmer, wetter weather may have caused the species to climb higher than usual. 

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“Our summer even this year has been warmer, it has been wetter, there has been more water even from snowpack this winter, and our mosquito populations have increased, thus increasing the risk of exposure to West Nile,” Senst said. “We shouldn’t assume that there’s no risk just because we’re up in the mountains.”

As the effects of climate change impact high-elevation ecosystems, the prevalence of vector-borne diseases is likely to increase. The county public health office tracks mostly tick-borne illnesses like Rocky Mountain Spotted Fever or Lyme disease — which is not endemic to the area. 

How to protect yourself

West Nile Virus is transmitted by mosquito bites and cannot be spread from person to person. According to the Centers for Disease Control and Prevention, most people infected with the virus do not feel sick. About 1 in 5 people who are infected develop a fever and other symptoms. About 1 out of 150 infected people develop a serious, sometimes fatal, illness.

Still, Stenst said the death rate is incredibly low, even amongst rare, neuroinvasive, severe cases. 

There is no treatment — apart from supportive care — nor vaccine for the virus, so public health officials say prevention is key.

The county recommends taking the following precautions to protect from mosquitoes, especially at sunrise and sunset — when mosquitoes are most active — and near standing or still bodies of water:

• Avoid gathering outside during sunrise and sunset
• Wear EPA-approved insect repellent (Examples: DEET or oil of lemon eucalyptus)
• Wear protective clothing such as long pants, long sleeve shirts, and closed-toed shoes

West Nile Virus can lead to serious illness and death in rare cases. The disease can present in two forms: West Nile Fever (less severe and more common) and a neuroinvasive form of illness (more severe and less common). Symptoms usually occur 3-14 days after being bit by an infected mosquito and include but are not limited to:

• Fever
• Fatigue
• Headache and/or neck pain
• Joint and muscle stiffness
• Muscle tremors
• Vision impairment 
• Paralysis or severe muscle weakness

Horses are particularly susceptible to severe illness from West Nile Virus. If they contract the virus, it can lead to permanent physical impairment or death. An equine vaccine is available and horse owners are encouraged to speak to their veterinarian regarding vaccination.

If you are feeling sick, contact your healthcare provider for testing and care options. If you are experiencing a medical emergency, please contact 911.