The Hawaii Department of Health on Wednesday confirmed an additional case of Legionnaires’ disease in a guest who stayed at The Grand Islander by Hilton Grand Vacations in Waikiki.

The individual — a visitor who stayed at the Grand Islander from March 18 to 25 — was diagnosed with Legionnaires’ disease on April 2.

The latest development comes about two weeks after DOH first announced it was investigating two cases of Legionnaires’ disease in guests following their stays at The Grand Islander.

The first case was diagnosed in June 2021 and the second one on March 6 or 7, 2022.

Following identification of the first two cases, the Grand Islander carried out mitigation measures as required by DOH on March 22. All three stayed there prior to these measures, DOH said.

“While it is not yet known how or where this individual was infected, our team is working cooperatively with the Hawaii Department of Health as an investigation is conducted,” said a spokesperson at The Grand Islander. “The health and safety of our owners, guests and team members is our top priority.”

DOH was first alerted to the potential for Legionella growth within the building’s potable water system via water samples collected from it.

DOH said additional analyses are ongoing, and that pinpointing a source of Legionella transmission is often difficult. For the time being, DOH is requiring additional testing and mitigation measures to remediate all possible water sources.

Legionnaires’ disease is a serious type of pneumonia caused by exposure to Legionella bacteria, which are found in freshwater environments, and can spread via water systems such as showerheads, sink faucets, cooling towers, hot tubs, decorate fountains, and large plumbing systems.

Symptoms include cough, shortness of breath, fever, muscle aches, and headache, and usually begin within two to 14 days of exposure.

Most healthy people exposed to Legionella bacteria do not develop Legionnaires’ disease, but those ages 50 and older, current or former smokers, and people with chronic lung disease or weakened immune systems are at increased risk.

The disease is treated with antibiotics, according to the U.S. Centers for Disease Control and Prevention.

People can get Legionnaires’ disease when they breathe in small droplets of water in the air that contain the bacteria, CDC said, but in general, people do not spread Legionnaires’ disease to other people.

Individuals who stayed at the Grand Islander and developed symptoms consistent with Legionnaires’ disease are encouraged to seek medical attention and report the illness to DOH’s Disease Reporting Line at 808-586-4586.