Four more human cases of West Nile virus have been confirmed by the Massachusetts Department of Public Health.
Three of the cases are in Middlesex County and one in Hampden County.
“Confirmation of these four cases is a timely reminder that people need to take the threat of mosquito-borne illness seriously no matter where they live,” state epidemiologist Al DeMaria said in a statement. “It’s vitally important that people take steps to protect themselves against mosquito bites.”
The most recent cases are prompting health officials to raise the West Nile threat level to “high” in Chelsea, Chicopee, Everett, Lexington, Malden, Medford, Melrose, Revere, Saugus and Winthrop.
The threat level is also being raised “moderate” in Bedford, Burlington, Holyoke, Lincoln, South Hadley, Stoneham, Wakefield, West Springfield, Winchester, and Woburn.
There have been four other confirmed cases of West Nile virus in Massachusetts residents this year. Last year, six cases were confirmed in the state.