In the Lenox Hill outbreak, where the patients are linked by geography, chances of finding the source may be better. Inspectors have looked at all cooling systems within about half a mile of the affected area, 116 in total, Dr. Bassett said. But results of the investigation will take up to two weeks — the bacteria must be cultured in a lab, and grow slowly, she said.
In the past, contaminated cooling systems have been identified as the source of outbreaks of Legionnaires’, including one in 2015, in the South Bronx, that killed 15 people and sickened more than 70. That outbreak was linked to rooftop cooling towers in the area. Recent, smaller outbreaks have been reported, including one last week, where the bacteria were found in the water systems of an East Harlem police station after an officer fell ill. The officer has since recovered, the Police Department said.
Each year, 200 to 400 cases of the illness are recorded in New York City, the health department said. After the 2015 Bronx outbreak, the city passed legislation requiring better monitoring of cooling towers. Since then, the health department said, it has monitored more than 6,000 towers for the bacteria, which flourish in warm water.
In an effort to discover the sources of infection, the department uses computer algorithms to determine links between cases and employs specially trained investigators to interview people who were infected.
People with depressed immune systems, those over 50 and smokers are particularly vulnerable to the bacteria, which cause symptoms similar to the flu or pneumonia and can be treated with a similar course of antibiotics.
“Legionnaires’ disease is completely treatable, and it has the best outcome when people are diagnosed early,” Dr. Bassett said.