The first case of a human infected with Eastern equine encephalitis this year has been found in Massachusetts, state Public Health Commissioner John Auerbach announced at a press conference yesterday.
A Rhode Island resident in his 20s is in critical condition after being exposed to the virus, Auerbach said at the press conference at the Jamaica Plain campus of the University of Massachusetts Medical School.
The Newport County resident was probably infected in one of the Southeastern Massachusetts communities that were designated for aerial mosquito spraying more than a week ago, Auerbach said.
“Unfortunately,’’ he added, “This gentleman was exposed about a week before the spraying.’’
Forty percent of those infected with the virus succumb to the illness, according to Auerbach.
“It’s a deadly illness and causes serious injury in those who survive,’’ Auerbach said.
Eastern equine encephalitis is transmitted to humans by the bites of infected mosquitoes. It typically affects people in the Atlantic and Gulf Coast areas of the country, according to the US Centers for Disease Control and Prevention.
Severe cases “begin with the sudden onset of headache, high fever, chills, and vomiting,’’ the CDC says. “The illness may then progress into disorientation, seizures, or coma.’’
There is no specific treatment for the virus, and care is determined by the symptoms in the infected individual, according to the CDC.
News of the infection comes a little more than two weeks after Governor Deval Patrick announced that public health officials would conduct aerial sprayings to combat diseased insects.
Southeastern Massachusetts is considered at high risk for the virus because of swampy terrain that attracts mosquitoes. Seventeen communities including Acushnet, Berkley, Bridgewater, Carver, Duxbury, Fairhaven, Freetown, Halifax, Kingston, Lakeville, Mattapoisett, Middleborough, New Bedford, Plympton, Raynham, Rochester, and Taunton were sprayed.
The treatment, which wiped out 80 percent of mosquitoes in the area, was considered successful, Auerbach said.
The victim, whose name was not released because of Rhode Island Department of Health policy, was the first case of the disease since fall 2008, when a 73-year-old Bay State resident was diagnosed.
Before the 2008 infection, 13 cases of the virus were reported in Massachusetts between 2004 and 2006. Six of those people died from the disease.
While yesterday was the first human case this year, the virus has been documented in at least one animal.
The Massachusetts Department of Health and Human Services released a statement last month that a 7-month-old horse became infected in Middleborough.
“The young stallion developed symptoms on July 20, deteriorated very rapidly and was euthanized on July 21,’’ the statement said.
Auerbach stressed that virus-carrying mosquitoes pose a serious health risk despite recent cool temperatures, and he urged residents not to let the weather lull them into a false sense of security. “People can’t let their guard down based on temporary changes in the temperature,’’ he said.