The man, who is older than 60, is the sixth person in the United States to be diagnosed with the disease this year, up from two in 2010. The disease is almost always fatal.

A Barnstable County man has become the first person since 1935 to contract rabies in Massachusetts and remained hospitalized in critical condition yesterday as disease trackers sought to confirm that he was infected by a bat in his home.

Rabies, spread through the saliva of infected animals, is caused by a virus that attacks the central nervous system. There is no evidence that the population of rabid animals in the state is growing, said John Auerbach, the state’s public health commissioner.


“This is not a reason for people to panic,’’ he said. “There is no elevated risk here.’’

Auerbach declined to be more specific about where the man lives or how he is being treated; because of patient confidentiality laws, the man’s identity is not being disclosed.

There had been bats in the man’s home, Auerbach said, and other members of the household are being treated with postexposure vaccinations.

No animals had been trapped or tested in relation to this case by yesterday morning, said Catherine Brown, state public health veterinarian. “We’re still investigating.’’

Rabies symptoms can be slow to develop, so the man may have been exposed to an infected animal six weeks ago or more, Brown said. Because of the small size of a bat’s teeth, it is possible for people who are sleeping or incapacitated to be bitten without knowing it.

The US Centers for Disease Control and Prevention will be able to use fluid samples taken from the Barnstable County man to conduct tests to determine the type of animal that bit him, said Charles Rupprecht, the agency’s rabies program director.


Auerbach said people should have bats removed that enter into their living space and consider installing a cap to prevent them from entering through the chimney.

Rabies infects tens of thousands of people globally each year, with rabid dogs being a primary agent of transmission. But the disease has been controlled in the United States since about the 1930s, when widespread vaccination of domestic animals began. The disease had disappeared from land animals, such as raccoon and foxes, in Massachusetts but reappeared in the 1990s.

Development in the 1980s of a highly effective vaccine for people who have been bitten, scratched, or otherwise exposed to a rabid animal further lessened human risk. State officials urged people who may have come in contact with an infected animal to thoroughly wash any wounds and see a doctor immediately. Hundreds of people in the state receive the series of shots each year, said Dr. Lawrence Madoff, director of the state Division of Epidemiology and Immunization.

But most who go untreated and develop rabies symptoms die from the disease. Flulike symptoms may progress to anxiety, delerium, hallucinations, paralysis, inability to swallow, a fear of water, or excessive salivation.

Of the six people diagnosed with rabies in the United States this year, three contracted the disease overseas. A 9-year-old girl infected in California survived. Four have died.


There have been cases of Massachusetts residents dying of rabies contracted abroad, including a Waltham man who died in 1983 after being bitten by a dog in Nigeria. But the Barnstable County man is the first in 76 years to contract the disease while in the state.

Rupprecht of the CDC called rabies a neglected disease. It has the highest fatality rate of any infectious disease, yet little is known about how the virus controls the nervous system and what can be done to treat it, he said.

Until recent years, there have been virtually no options to help patients with rabies, said Dr. Rodney Willoughby, an infectious disease specialist at Children’s Hospital of Wisconsin.

“This used to be considered 100 percent fatal, and the recommended protocol was to isolate them in a dark room and let them die,’’ he said.

Willoughby and others at the hospital developed an improvised protocol to treat 15-year-old Jeanna Giese, who was admitted to the hospital with rabies in October 2004,

His team knew that rabies did not attack the brain itself but affected communication within the nervous system in such a way that it caused the patient’s death. So, they tried turning off that communication system, keeping their patient heavily sedated while her body worked to clear the infection. The girl survived.


“She’s now out of college and doing well,’’ Willoughby said in an interview yesterday.

Since then, the treatment has been used on 36 people around the world, including the California girl this year. Five have survived, with the success rate growing as doctors learn more and tweak the protocol, said Willoughby. He expects that, someday - “maybe sooner than later’’ - as many as 60 percent of patients with full-blown rabies will survive.

The CDC’s Rupprecht cautioned against such optimism, saying that much is unknown about the disease and that prevention remains the most effective way to fight it.

Chelsea Conaboy can be reached at cconaboy@boston.com.