Eastern Equine Encephalitis (EEE) & West Nile Virus (WNV)

August 28, 2018

A horse in the Chesapeake Health District was recently diagnosed and died because of eastern equine encephalitis.  As a precautionary measure, we are providing you informational material that can serve as a guideline in implementing protective measures against West Nile Virus (WNV) and Eastern Equine Encephalitis (EEE).

August and September are the most active months for cases of mosquito-borne diseases, including eastern equine encephalitis (EEE) and West Nile virus (WNV). “School may signal the beginning of fall for many people, but NOT for mosquitoes. This is the time of year residents should be most cautious about eliminating mosquito breeding sites and avoiding excessive mosquito bites,” said Dr. Nancy Welch, director, Chesapeake Health Department. “Mosquito control districts all over Hampton Roads are detecting higher than normal WNV activity in mosquitoes this season.”

Although WNV mosquitoes are more numerous and infectious this year, the nuisance mosquitoes so prevalent in the rural areas of the city are not disease carriers. “Many of our service requests are in response to very fast developing and aggressive mosquito species. They are the biggest nuisance and we are spraying in response to high numbers, but they do not pose a disease risk,” said Dreda A Symonds, director, Chesapeake Mosquito Control Commission. “WNV mosquitoes are most active 1 hour after sunset and are most common in the suburban areas of the city.”

People at highest risk for serious mosquito-borne disease are young children, adults 50-years-old or older, and those whose immunity is suppressed because of a disease such as cancer or diabetes. Anyone experiencing symptoms such as high fever, severe headache, stiff neck, confusion and lethargy should seek medical attention right away.

The Chesapeake Mosquito Control Commission has been actively working to reduce mosquito populations to lower the risk of mosquito-borne diseases to humans and animals.  Horse owners have been notified in the areas where positives have occurred and have been strongly encouraged to vaccinate their animals.

Although mosquito-borne diseases can lead to severe illness in humans, less than 1% of those infected develop serious neurological problems. The best prevention for these diseases is to avoid mosquito bites. Following are tips that can help reduce the risk of being bitten.

  • Use insect repellent containing an EPA-registered active ingredient. Follow directions on the label.
  • Many mosquitoes are most active at dusk and dawn. Be sure to use insect repellent and wear long sleeves

and pants at these times or consider staying indoors during these hours.

  • Make sure you have good screens on your windows and doors to keep mosquitoes out.
  • Eliminate mosquito-breeding areas in your yard where rainwater collects. Turn over or empty bird baths, flower pots, buckets, or barrels. Clean roof gutters and downspout screens. Remove old tires from your yard.   Eliminate standing water on flat roofs, boats or tarps. Keep children’s wading pools empty and on their sides when not in use.

If you cannot get rid of the standing water, put larvicide, such as Mosquito Dunks, in the water to kill developing mosquitoes. Be sure to read the instructions on the label.

For more information on mosquito bite prevention, visit

To report a mosquito problem in Chesapeake, visit http://www.cityofchesapeake.net/

People concerned about or experiencing these symptoms should contact their physicians immediately.

If you have any questions, please feel free to contact the Chesapeake Health Department, 382-8642 or Chesapeake Mosquito Control at 382-3450.