The mosquitoes return to Vermont in spring, but do not typically pose a health risk until the summer months.
By July, some mosquitoes may be carrying West Nile virus (WNV) or Eastern equine encephalitis virus (EEE), and it will be important for Vermonters to take precautions to prevent mosquito bites.
West Nile virus (WNV) and Eastern equine encephalitis virus (EEE) can cause illness in people and some animals. WNV has been found in all counties in Vermont. EEE virus has so far caused illness in only a few areas of Vermont, but not as much is known about this virus in the state, and it is likely to be found in additional areas.
Mosquito surveillance for these diseases begins in mid to late June. Surveillance findings are posted on this website.
Department of Health West Nile virus/EEE information line:
1-800-913-1139 • Monday through Friday • 8:00 a.m.- 4:30 p.m.
West Nile Virus
West Nile virus (WNV) is a mosquito-borne virus that can cause illness ranging from a mild fever to more serious disease. WNV was first identified in the United States in 1999 and detected in Vermont in 2000. WNV continues to cause a few cases of illness in people and animals each year.
Eastern Equine Encephalitis
Eastern equine encephalitis (EEE) is a rare but serious disease, also caused by a virus. The first two human cases reported in Vermont occurred in 2012. The disease most commonly affects people and horses, but illness has been reported in other animals including alpacas, llamas, donkeys, pheasants and emus.
Information Resources and Materials
Fact sheets, brochures, booklets, posters and education materials.
Surveillance and Data
Includes ongoing and historical data, test results, risk assesments and maps, and the Vermont Surveillance and Response Plan.