A downtown Atlanta hotel has closed its doors while officials test for a rare, and sometimes deadly, form of pneumonia.

Six people who stayed at the Sheraton Atlanta on Courtland Street tested positive for Legionnaires’ disease, which is contracted by breathing in mist or swallowing water containing bacteria. Public health officials have not yet confirmed if the guests contracted the disease during their stay, a spokeswoman for the hotel said.

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“The health and safety of our guests is our greatest priority,” general manager Ken Peduzzi said in a statement. “We are working closely with public health officials and outside experts to conduct testing to determine if legionella is present at the hotel. As a result, out of an abundance of caution we have made the decision to close the hotel while we await the results.”

Sheraton was working Monday to relocate about 450 guests to nearby hotels. Peduzzi said they were also reaching out to guests with upcoming reservations to help them find other accommodations. Guests whose reservations are canceled will receive a full refund, he said.

Testing and remediation is being conducted by a Legionella consultant at the hotel’s expense, according to the Georgia Department of Public Health. Once complete, the agency and the Fulton County Board of Health staff will work with the hotel on next steps.

“There currently are (six) confirmed cases of Legionnaires’ disease,” Nancy Nydam, a spokeswoman for the state health department, said in an email. “Contact investigations with other people who stayed at the hotel are ongoing. Legionnaires’ is a reportable condition in Georgia, so by law cases must be reported to public health.”

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According to the Atlanta-based Centers for Disease Control and Prevention, the Legionella bacteria is found naturally in freshwater environments, like lakes and streams, but it can become a health concern when it multiplies and spreads through human-made water systems. The bacteria can get into showerheads and sink faucets, plumbing systems and even decorative fountains and water features.

About one in 10 people who come down with Legionnaires’ disease die due to complications from their illness, the CDC said. One in four who contract the disease while staying in a healthcare facility will die, as their immune systems are already compromised.

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It is more common for people to get Legionnaires’ through breathing in small droplets of water in the air than by drinking contaminated water, according to the CDC.

The disease got its name after a 1976 outbreak at an American Legion convention in Philadelphia. Of the more than 2,000 members who attended the convention of the veterans organization, 182 came down with a serious, atypical form of pneumonia and 29 died.

Theirs were the first recorded cases of Legionnaires’ disease, also called Pontiac Fever after a 1968 outbreak in Pontiac, Michigan. It wasn’t until after the 1976 outbreak that health officials were able to determine the same kind of bacteria caused both diseases, according to the CDC.