Legionnaires' Outbreak: What We Know

What has caused the outbreak?

Legionnaires' Disease is not spread person to person. People in the South Bronx became sick by breathing in contaminated mist, mostly likely from cooling towers on the roofs of commercial buildings.

These cooling towers can be breeding grounds for legionella pneumophila, the bacteria that causes the disease, particularly if the towers are not maintained properly.

The city identified five cooling towers in the area that tested positive for legionella. All five of those sites have been cleaned, according to city health officials. 

State health officials said Thursday that they found a sixth site that tested positive for contamination.

Who is getting sick?

As of Thursday, there were 100 cases of people with Legionnaires' Disease in the South Bronx. Ten people have died. 

The people infected during this outbreak range in age from 30 to 80 years old. The median age is 55. 

The city has said that people with pre-existing medical conditions are more vulnerable to Legionnaires' Disease, and the South Bronx is a community with chronic health issues.

Of those infected in this outbreak, underlying medical issues include diabetes, lung diseases and chronic use of alcohol, cigarettes or illicit drugs, according to city health officials.

Officials say Legionnaires' Disease is highly treatable, but early detection is key. Thirty-one-year-old Daniel Tejada was hospitalized — the first time in his life — for more than three weeks as he was being treated for the disease, according to his cousin Annie Minguez, after he tried for days to "sweat out his fever." And Neil Pariser, a 67-year-old city planner, told WNYC he was initially sent home from the hospital when doctors did not diagnose his flu-like symptoms as Legionnaires. When his conditions worsened days later, he was hospitalized for more than a week.

What are cooling towers, and why are they susceptible to legionella bacteria?

It takes a lot of energy to cool interior spaces, and you need something to cool the machinery. Smaller air-conditioning units are cooled by air or fans. The larger units used by big commercial and residential buildings are usually cooled by water. But the water used to cool the machinery itself becomes warm, and various organisms, including legionella bacteria, often begin to grow. Well-maintained chemical and filtration systems and periodic cleaning suppress bacteria to levels that do not harm people. Typically, building owners hire professional services to perform maintenance. If they do the job correctly, there shouldn't be problems, but all cleanliness regimes are subject to human error.

What regulations around cooling towers exist?

There are widely accepted guidelines and standards, but no legal regulations in New York City or any other city or state. 

Mayor Bill de Blasio said this week that his administration and the City Council will introduce legislation to better monitor cooling towers, including creating a registry of them. Although the city requires permits to install such units, it does not have any comprehensive way of locating them.

On Thursday, Mary Bassett, the city health commissioner, issued an order requiring that all owners of buildings with cooling towers get these towers tested and disinfected within the next 14 days. Failure to comply with the order is a misdemeanor.

If building owners have already had cooling towers disinfected within the last 30 days, they can present this paperwork to the city.