Locally Acquired West Nile Virus Infection Identified in a Maine Resident

Sep 17, 2024

Recent positive tests found in animals demonstrates increased human risk

AUGUSTA-- The Maine Center for Disease Control and Prevention (Maine CDC) announced today the detection of West Nile virus (WNV) in a Maine resident.

The case was found in a Cumberland County resident in their 40s with no history of recent travel outside of the state, leading health officials to believe it was locally acquired. This is the first locally acquired WNV infection detected in a Maine resident since 2020 and the second Maine resident to become infected with WNV this year. The results are presumptive while awaiting confirmation by the U.S. Centers for Disease Control and Prevention laboratory.

WNV, along with Eastern Equine Encephalitis virus (EEE) and Jamestown Canyon virus (JCV), are viruses spread through the bite of an infected mosquito. EEE, WNV, and JCV usually start with flu-like symptoms in humans. Severe symptoms can include brain swelling (encephalitis) and spinal cord inflammation (meningitis). About one out of 150 people infected with WNV may develop a serious, sometimes fatal illness. For survivors, recovery may take several weeks to months, and some will have lifelong impacts. EEE, by contrast, is far deadlier with an approximate mortality rate of 30 percent for those who develop severe disease and, if survived, often has serious, lifelong neurological impacts. If you experience flu-like symptoms, severe headache, behavior changes, or serious drowsiness, call a health care provider, especially if a COVID-19 test is negative.

WNV, EEE, and JCV cannot spread from human to human or human to animal. The risk of mosquito bites is highest from dusk to dawn and when temperatures are above 50°F. This is when mosquitoes are most active and biting.

The Maine CDC's health and environmental testing laboratory (HETL) tests animals and mosquitoes for EEE, JCV, and WNV. Already this year, the Maine CDC has reported:

• EEE in 4 horses, 2 emus, 1 llama, and 1 wild turkey
• JCV in 4 mosquito pools (groups of up to 50 mosquitoes regularly tested as part of routine surveillance)
• WNV in 15 wild birds

Due to recently detected positive results, there is currently a high risk to people living in Cumberland, Kennebec, Penobscot, Somerset, and Waldo counties. All other counties are at an elevated risk at this time.

"One person has now tested positive for locally acquired WNV and four domestic animals tested positive for EEE just last week," said Maine CDC Director Dr. Puthiery Va. "Maine people know that mosquitoes are a nuisance, but we want people to be aware that they can also potentially lead to serious consequences for your health. Whether mowing the lawn, walking the dog, or enjoying a meal outside, we want all Maine people to remember to take precautions against mosquito bites whenever you go outside."

When going outside, consider taking these steps to protect yourself from EEE, WNV, and JCV:

Avoid Mosquito Bites

• Apply Insect Repellent when Outdoors. Use a repellent with an EPA-registered ingredient, such as DEET, IR3535, permethrin, picaridin (KBR 3023), or oil of lemon eucalyptus (p-menthane-3,8-diol (PMD)) according to the instructions on the product label.
• Be Aware of Peak Mosquito Hours. The hours from dusk to dawn are peak biting times for many mosquitoes. Consider rescheduling outdoor activities that occur during evening or early morning in areas of high risk.
• Wear Clothing That Can Help Reduce Mosquito Bites. Wearing long sleeves, long pants and socks when outdoors will help keep mosquitoes away from your skin.

Mosquito-Proof Your Home

• Drain Standing Water. Mosquitoes lay their eggs in standing water. Limit the number of places around your home for mosquitoes to breed by draining or discarding items that hold water. Check rain gutters and drains. Empty unused flowerpots and wading pools and change the water in birdbaths frequently.
• Install or Repair Screens. Keep mosquitoes outside by having tightly fitting screens on all windows and doors.

Protect Your Animals

Animal owners should reduce potential mosquito breeding sites on their property by eliminating standing water from containers such as buckets, tires, and wading pools -- especially after heavy rains. Water troughs provide excellent mosquito breeding habitats and should be flushed out to reduce mosquitoes near paddock areas.

Horse owners should keep horses in indoor stalls at night to reduce their risk of exposure to mosquitoes. Owners should also speak with their veterinarian about mosquito repellents approved for use in animals and vaccinations to prevent WNV and EEE.

For more information:

• Find mosquito surveillance reports.
• View answers to frequently asked questions.
• Learn about repellents.

Maine CDC Director, Dr. Puthiery Va will be available for interviews. To schedule, please contact DHHS Press Secretary Lindsay Hammes.