Legionnaires’ Disease Sickens 22 in New York. Here’s What to Know.

At least 22 people have fallen ill, including one person who has died, from Legionnaires’ disease in New York City over the last two weeks, according to the city’s health department.

City health officials believe that the people most likely became ill after breathing in bacteria sprayed from a cooling tower in central Harlem. (Cooling towers help regulate building temperature.) The city health department said in a news release on Wednesday that it was testing the cooling towers in the area and continuing to investigate the outbreak.

What are the symptoms of Legionnaires’ disease?

People usually develop symptoms between two days to two weeks after breathing in Legionella bacteria. That bacteria naturally occurs in streams, creeks and lakes, but it can rise to dangerous levels in warm, artificial environments such as hot tubs, humidifiers, fountains, pools and cooling and water systems.

Early symptoms tend to resemble those of the flu: fever, chills, muscle aches, headaches, dry cough and shortness of breath. People with Legionnaires’ also sometimes develop gastrointestinal symptoms like nausea and diarrhea, said Dr. Emily Abdoler, a clinical associate professor of infectious diseases at Michigan Medicine.

Who is at higher risk?

Most healthy people who are exposed do not get sick, but certain groups are at higher risk, including people who are 50 and older; current and former smokers; and people with weakened immune systems or chronic conditions such as cancer, lung disease, diabetes or kidney and liver failure.

Legionnaires’ tends to worsen during the first week or so. In severe cases, Legionnaires’ patients may be hospitalized and require oxygen treatment. People who are seriously ill can develop lung failure and heart damage. About one out of every 10 people who gets sick with Legionnaires’ will die, according to the Centers for Disease Control and Prevention.

Is it contagious?

You cannot get Legionnaires’ from other people. It commonly spreads through mist or vapor that contains the bacteria. Several outbreaks have been linked to cooling towers in big cities. In rare cases, you can contract the disease from breathing in contaminated soil.

How is Legionnaires’ treated?

Doctors prescribe antibiotics. The sooner someone starts antibiotics, the more effective the treatment will be, said Dr. Ben Singer, a pulmonary and critical care specialist at Northwestern Medicine. Most people who take antibiotics will recover from the disease, but some can continue to feel certain symptoms for months.

“Any pneumonia can cause a lingering type of fatigue,” Dr. Singer said. “People can take a long time to get better.”