The Nova Scotia Health Authority says there is now an outbreak of legionnaires' disease, after two more cases were confirmed in Dartmouth, bringing the total number of confirmed cases to three.

Dr. Gaynor Watson-Creed said three people who live at the Alderney Manor apartment building have tested positive for the legionnella bacteria.

That meets the definition of an outbreak, she said Friday.

Residents of Alderney Manor in Dartmouth are worried that there may be legionella bacteria in their building. (Stephanie vanKampen/CBC)

"Although it is helpful to know that the laboratory results support our initial suspicions, we will continue to look at additional cases of pneumonia in Dartmouth with suspicion for the next while," said Watson-Creed, one of the province's medical officers of health.

While more people in the Dartmouth area are having themselves checked for legionnaires' disease because of this, Watson-Creed doesn't expect many people will have it.

"We have a lot of people searching. We have an increase in testing as a result of that, but often a number of cases from that won't pan out," she said.

From the beginning, officials treated the investigation as an outbreak to err on the side of caution because test results on the building's heating and cooling system could take weeks to come back.

Actions at Alderney Manor

Crews have not yet confirmed the source. Watson-Creed says they may use a flush system with chlorine or super-heating system to kill the bacteria in the building's pipes.

Watson-Creed, who will meet with Alderney Manor residents later on Friday, said a number of pneumonia cases have been identified in Dartmouth and each case is being tested for legionnaires' disease.

"It is quite possible that as the investigation continues, more people will be identified," she said.

Symptoms of the disease — a severe form of pneumonia — includes fever, chills, muscle aches and diarrhea. It's more common among older people and in 15 per cent of cases, it can be fatal.