One of the four patients with Legionnaires’ disease at the Queen’s Medical Center has died, according to the state Department of Health.

The Health Department notified providers of the death this morning in a medical advisory and said two of the four patients had similar exposure and two others were completely unrelated. The two related cases may have been hospital-acquired, said state epidemiologist Sarah Park, who is investigating the cases.

Of the remaining three, one patient has recovered and two are still hospitalized and being treated for both legionellosis and other underlying conditions. All four cases were among patients well over the age of 50 and who had other serious medical conditions, the memo said.

The string of cases caused by a bacterial infection was alarming enough for Queen’s and the state Department of Health to issue a news alert Tuesday ensuring the public that health officials are “working closely with the Centers for Disease Control and Prevention to investigate these cases and all potential sources of Legionella exposure within and outside of the hospital.”

Queen’s said it is taking additional precautions to keep high-risk patients who are at greatest risk of contracting the disease away from tap water in any form at the hospital. Legionnaires’ disease is primarily spread through inhaling aerosolized water droplets.

While Legionella is naturally found in freshwater lakes, streams and soil, it is a public health concern when spread in building water systems like shower heads and faucets, hot tubs and cooling systems. The disease is not readily transmissible from person to person.

Most people do not become ill when exposed to the bacteria, but those with compromised immune systems are particularly vulnerable to developing Legionnaires’ disease, which is serious because it has a higher fatality rate than other types of pneumonia.