Health officials in New York City said on Friday that they had identified two city-owned sites, including Harlem Hospital, as the sources of an outbreak of Legionnaires’ disease that had killed seven people and sickened over 100 more in recent weeks.
Water samples taken from cooling towers at the hospital and a nearby construction site of a new public health lab were found to contain Legionella bacteria that shared genetic traits with samples taken from patients, Dr. Michelle E. Morse, the city’s acting health commissioner, said at a news conference on Friday.
The towers were among 12 spread over 10 buildings in Central Harlem where traces of Legionella had been found after the outbreak was first detected last month.
All 12 towers were disinfected while further lab testing was conducted on the samples, which led to a decline in the number of new cases, health officials said. On Friday, Dr. Morse said the city had declared the Harlem outbreak over because there had been no new cases connected to that cluster since Aug. 9.
Health officials said on Friday that the city had proposed new policies in response to the outbreak, which had killed seven people, sickened 114 and led to the hospitalization of 90. Six people remained hospitalized as of Friday, officials said.
“New York City has among the most rigorous and protective legislation on cooling towers in the nation, but the reality is when you try to control nature it is very difficult work,” Dr. Morse said. “Even so, moments of this demonstrate that our system can always be improved.”
The proposed policies include requiring building owners to test for Legionella every 30 days instead of 90, and increasing the number of Health Department employees who conduct inspections and respond to outbreaks.
“It is an issue of providing the resources and making the reforms that from this experience we deem necessary and appropriate,” said Randy Mastro, the city’s first deputy mayor. “We aim to prevent any spread of Legionnaires’ disease from occurring. Obviously, there was a spread that occurred here.”
Legionnaires’ disease is a form of pneumonia that is caused by certain common species of Legionella bacteria. Each year, between 200 and 500 people in New York City are diagnosed with the illness and about a dozen die, although large outbreaks traced back to a single source are less common.
The construction site linked to the outbreak was a city-owned property under contract with Skanska, a multinational construction firm that has been building a new public health lab for the city, Dr. Morse said.
She said the site had a cooling tower that had not been registered with the Health Department, but that a team from the agency had taken a sample from the tower on July 28 and ordered it to be disinfected soon after.
Harlem Hospital appeared to have been up to date on all of its inspections and in compliance with city rules, said Dr. Mitchell Katz, the president of NYC Health + Hospitals, which runs the facility.
He said the hospital’s cooling towers had been inspected for Legionella multiple times, and by several methods, over the past year. But the bacteria is “ubiquitous” in the environment, especially during the summer months, he said. That meant no amount of testing could guarantee that it would not appear in the warm stagnant water of a cooling tower’s tank.
Furthermore, Dr. Katz said there were limits to how aggressively one could disinfect the towers, which play critical roles in cooling systems. Warm water is piped to the rooftop towers, where fans then cool the water through evaporation, sending mist into the air.
If you add too much disinfectant into the system, he warned, the mist could carry chemical irritants, leading to allergic reactions or other negative health effects among passers-by.
“I support more frequent testing and also a certain amount of humility about nature and ubiquitous organisms that like standing water in warm weather and the limitations of the cooling towers that are cooling the air we breathe,” said Dr. Katz. “You cannot over-chemicalize that air.”
Liam Stack is a Times reporter who covers the culture and politics of the New York City region.
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