The Maine Center for Disease Control and Prevention is investigating the connection between four reported cases of Legionella in the Bangor area.

All four patients were hospitalized with the illness, also known as Legionnaires’ disease, Maine Center for Disease Control and Prevention spokesman Robert Long said in a statement. Two remain hospitalized. The cases were confirmed recently, but no specific timeline was provided.

The Maine CDC is attempting to determine if the infections are coincidental or if there is a common exposure. The Maine CDC did not provide additional details on how the cases could possibly be linked.

Health care providers in the area have been notified about the four cases so that they can consider testing for the illness. All cases have to be reported to the Maine CDC.

Legionella is not spread from person to person. Legionella bacteria are found naturally in freshwater environments such as lakes and streams. Persons can become infected by breathing in droplets of water that contain the bacteria, a concern that intensifies when the bacteria grow and spread in a building’s water system such as cooling towers used in air-conditioning systems, hot tubs, fountains and large plumbing systems.

Legionnaires’ disease is a type of pneumonia. Symptoms include cough, shortness of breath, fever, muscle aches and headaches. A doctor will use chest X-rays or a physical exam to check for pneumonia and also may order tests on a sample of urine or sputum to determine if a lung infection is caused by Legionella.

Most healthy people who are exposed to Legionella do not get sick, but those at increased risk of getting sick are people over 50, current or former smokers, people with a chronic lung disease, weakened immune systems or cancer. Others at risk include individuals with underlying health conditions such as diabetes, kidney failure or liver failure.

Legionnaires’ disease is treated with antibiotics and most people who get sick will need hospital care. Most people make a full recovery, but about 1 in 10 people die from the infection.

Cases have been on the increase in the United States since 2000. About 9,000 cases were reported in 2019. Maine has had an average 21.4 cases per year since 2016, according to the Maine CDC.

Health officials recommend taking preventive steps to limit the risk of bacteria growth in buildings. Electric water heaters should be flushed each year by a plumber, showers heads should be removed and cleaned on a regular basis, and humidifiers should be cleaned and disinfected.

Legionella was discovered after an outbreak in 1976 among people, who attended an American Legion convention in Philadelphia, according to the federal Centers for Disease Control and Prevention.