Students and residents of the Pioneer Valley are being advised to take precautions to prevent mosquito bites after a case of the mosquito-borne illness Eastern equine encephalitis was confirmed in the area on Thursday.

The threat of EEE is considered high in Amherst, as well as the surrounding towns of Granby, Pelham, New Salem, South Hadley and Ware, and critical in Belchertown, according to the Massachusetts Department of Public Health’s website.

The risk is highest in Belchertown, where a horse died from EEE on Aug. 31, according to an article in the Daily Hampshire Gazette. Initially, officials assumed the animal died of rabies, but further testing proved it to be a case of EEE.

On Friday afternoon, the University of Massachusetts sent an email out to all students, faculty and staff informing them of the advisory.

“We thought it was wise and important to inform students,” said University spokesman Ed Blaguszewski.

The email urged people to wear insect repellent and protective clothing, as well as avoid outdoor activity from dusk until dawn, when mosquitoes are most active.

People should choose an insect repellent that contains DEET, according to the Massachusetts Department of Public Health. Repellents containing permethrin, picaridin or IR3535 are also effective, according to the department.

Blaguszewski said that repellent is available for sale at the University Health Service’s pharmacy.

EEE is a rare disease carried by mosquitoes that can be fatal. There is no vaccine available to humans who have been infected by the disease, according to an EEE fact sheet written by the Department of Public Health.

In Massachusetts, there have been fewer than 100 cases of disease since it was discovered in 1938, according to the Department of Public Health. From 2004 to 2006, there were 13 cases of EEE outbreaks – six of them were fatal. Those that survive usually suffer permanent damage, according to the fact sheet.

Symptoms of the disease start appearing three to 10 days after an infectious mosquito bite. Early symptoms include a fever of 103 to 106 degrees, stiff neck and lack of energy. In later stages, the infected person will experience brain swelling and may go into a coma, according to the Department of Public Health

Katie Landeck can be reached at [email protected].