“While we now have a confirmed WNV case in a Newton resident, we have known about positive mosquitoes in Newton since July,” said Dr. Dori Zaleznik, commissioner of Health and Human Services for the City of Newton.

The patient, a Newton woman in her 50s, was recovering after a brief hospitalization, the Massachusetts Department of Public Health said in a statement.

A fourth human case of West Nile virus in the state was confirmed, and more possible cases were awaiting confirmation on Wednesday, health officials said.

After the detection, the West Nile virus threat level was raised to high in Newton and to moderate in neighboring Needham, Waltham, Wellesley, and Weston, officials said.


As West Nile infections spread across the state, health officials awaited confirmation on six more probable cases: four people in Middlesex County, one in Hampden County, and one in Essex County, the statement said.

“With today’s announcement, it’s clear that the threat of mosquito-borne illness is present throughout the Commonwealth,” said Dr. Al DeMaria, DPH state epidemiologist, in the statement.

Officials predict Massachusetts is on the verge of having the greatest number of West Nile virus-positive mosquito pools since the disease was first seen in the Bay State in 2000.

This season, two people in Middlesex County and one in Berkshire County had already been diagnosed with the virus, and West Nile-infected mosquitoes have been detected in 93 communities from nine counties.

Last year, there were six cases of the disease in Massachusetts residents and one case in a horse, according to officials.

With Labor Day festivities approaching, officials are urging people to take precautions.

Those include applying insect repellent, avoiding outdoor activities during the mosquito peak hours of dusk to dawn, covering exposed skin, and taking measures to keep mosquitoes out of the house.

Melanie Dostis can be reached at melanie.dostis@globe.com.