All three remain in stable condition and are expected to fully recover, said nursing home and state health officials. No one else at the facility has tested positive for Legionnaires' disease, they said.

State public health officials refused to characterize the three cases as an outbreak.

Legionnaires' disease, a form of pneumonia, spreads through inhaled water droplets, often originating in plumbing tracts or air- conditioning ducts. Country Gardens has no centralized air conditioning, and last weekend officials there pumped 160-degree water through the plumbing system for three hours - enough to kill any remaining bacteria.

Country Gardens officials made public their employee's Legionnaires' infection Sunday and disclosed the cases involving the two residents a day later.

"They're all doing fine," said Dotty Guenther, Country Gardens's administrator, who refused to disclose their names.

Both residents are in their 80s, said public health officials, and remain under observation at the nursing home, while a nearby hospital cares for the stricken employee, whose infection was the most virulent of the three. They are all being treated with antibiotics.

About half the residents at Country Gardens have Alzheimer's disease, a debilitating neurological disorder that often leads to pneumonia. Respiratory troubles, therefore, are a fact of life at Country Gardens. As a precaution, Guenther had all patients with breathing difficulties tested for Legionnaires' disease, and none tested positive.

In addition, numerous spots around the nursing home, including all water spigots and pipes, were swabbed for signs of the bacteria; test results are due later this week, according to state public health officals.

Country Gardens has contracted with a private industrial hygiene company for assistance in cleaning and sanitizing the entire facility, with a focus on the plumbing system, said Guenther.

Massachusetts averages 17 cases of Legionnaires' disease annually, according to public health statistics.

The disease begins with breathing difficulties and flu-like symptoms. It can soon cause intense fever and delirium. Up to 15 percent of the 8,000 to 18,000 annual US cases are fatal.

The elderly have slightly higher than normal risks of contracting Legionnaires' disease. Nursing homes such as Country Gardens are generally well prepared to deal with cases of the disease.

"The facility has been very proactive," said Roseanne Pawelec, spokeswoman for the state Department of Public Health, which is monitoring the situation.

In Lebanon, N. H. , last weekend, US Postal Service officials disclosed that a mail carrier had been diagnosed with Legionnaires' disease. He is expected to recover fully, they said.

Officials said the Lebanon case is unrelated to the Swansea infections.