The Massachusetts Department of Public Health (DPH) announced the fourth human case of West Nile virus (WNV) in the state this year. The individual is a male in his 80s who was exposed to the virus in Middlesex County in an area already known to be at increased risk. The risk of human infection with WNV is moderate to high in the Greater Boston area.
In 2021, there were 11 human cases of WNV infection identified in Massachusetts. WNV is usually transmitted to humans through the bite of an infected mosquito. While WNV can infect people of all ages, people over the age of 50 are at higher risk for severe disease. Most people infected with WNV will have no symptoms. When present, WNV symptoms tend to include fever and flu-like illness. In rare cases, more severe illness can occur. No human or animal cases of Eastern equine encephalitis (EEE) have been detected so far this year in Massachusetts.