Mosquito borne disease activity is still alive and well in Massachusetts as state health officials reported a human West Nile virus (WNV) case and an animal case of Eastern Equine Encephalitis (EEE) this week.

West Nile virus
Culex quinquefasciatus

The 4th human WNV case in the state, according to state health officials, is also the 4th case from a resident from Middlesex County.

The latest case is between 41 and 50 years old and was diagnosed on Sept. 28, according to reports.

In addition, Massachusetts Department of Public Health (DPH) today announced the second case of Eastern Equine Encephalitis (EEE) infection detected in a mammal this year. The infection was found in a five year-old horse from Westminster, a town located in Worcester County. The horse had to be euthanized due to the severity of her illness.

This finding will raise the EEE risk level in Westminster to “Critical.” The surrounding towns Fitchburg, Leominster, Princeton, Hubbardston, Gardner and Ashburnham will be raised to “High.”  Although these risk levels come with a recommendation to reschedule evening outdoor events, the weather will generally be cool enough that mosquito activity will be minimal.

“Infected mosquitoes continue to be present in our environment and will be around until the first hard frost,” said DPH State Public Health Veterinarian Dr. Catherine Brown. “Although mosquitoes are much less active when temperatures are below 60 degrees, the detection of EEE in a mammal should remind residents to take precautions when outdoors. Use insect repellant, cover up exposed skin, and avoid outdoor activities at dusk and night time, when mosquitoes are at their most active.”

There have been no human cases EEE so far this year. There have been four human cases of West Nile virus (WNV). Last year, there was one case of EEE acquired by a Massachusetts resident. EEE is spread to humans through the bite of an infected mosquito. EEE is a serious disease in all ages and can even cause death. For more infectious disease news and information, visit and “like” the Infectious Disease News Facebook page