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What caused the Legionnaires’ disease outbreak in NYC?

New York is facing the largest outbreak of Legionnaires' disease in its history: eight people have died from the respiratory illness since early July, and nearly 100 cases have been reported. Hari Sreenivasan learns more from Dr. Anne Schuchat of the Centers for Disease Control and Prevention.

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    New York City is facing the largest outbreak of Legionnaires' disease in its history.

    The airborne respiratory disease has killed 10 people since early July, with 100 cases reported. So far, it's been limited to the city's South Bronx neighborhood.

    Hari Sreenivasan picks up the story from our New York City studios.


    The disease is often characterized as a severe form of pneumonia. And it appears that water cooling towers have been a breeding ground for the bacteria that causes it. Legionnaires is rarely the focus of much public attention, but there were more 4,500 cases in the U.S. in 2013.

    Let's get some further information about the disease itself, the outbreak and the risks to people.

    Dr. Anne Schuchat is the director of CDC's National Center for Immunization and Respiratory Diseases. She joins me now from Atlanta.

    So tell me, first of all, what does this do to the body?

    DR. ANNE SCHUCHAT, Centers for Disease Control and Prevention: Legionnaire's disease is a form of pneumonia. It can cause fever, cough, difficulty breathing and other complications.

    It's one of the more severe pneumonias. And we think between 5 percent and 30 percent of people who develop Legionnaires' disease can have fatal infections.


    And how widespread is it? That 4,500 number is probably not something people are familiar with.


    Well, actually, we think there is under-reporting.

    So, based on some studies that we have done, we think there are probably between 8,000 and 18,000 cases of Legionnaires' disease each year in the United States. Many of them don't get diagnosed specifically. They're just treated as pneumonia, and even those that do get diagnosed may or may not get reported to the public health authorities.


    And how is it spread? In this particular case, we have been focusing on cooling towers, but what's the more likely mode or most likely modes of transmission?


    Well, it's really important for people to know that Legionnaires' disease is not spread person-to-person.

    Many kinds of pneumonia are caused by bacteria that are spread person-to-person, but Legionnaires' disease is caused by inhaling mist or vapors that have the bacteria in them. The Legionella bacteria that causes this pneumonia is found in the environment. It can be found in freshwater, but it can also be found in water in built — in the built environment.

    And when the bacteria grows to high levels and is blown around through mist or aerosolization, people can breathe it in. Most people who come in contact with this bacteria don't get sick, but the disease is particularly a problem in people who are smokers, people who have chronic lung disease, people who are elderly, or people who have other medical conditions that weaken their immune system.


    So, the cooling towers in this particular case, is it normal to see a cluster of buildings this close together or in a particular neighborhood? Or does it happen in different parts of the city or different parts of an area?


    You know, cooling towers are linked to about 40 percent of the outbreaks that we investigate, and they're associated with about 60 percent of the cases in all the outbreaks that we investigate.

    So cooling tower outbreaks tend to be a bit bigger than the outbreaks that are from potable water systems in buildings. But it's important to say that just finding the Legionella bacteria in the environment doesn't necessarily mean that that's the place where the infection is coming from. You know, the health departments in the area are doing intensive investigations to understand the exposures that are contributing to disease.

    What is often done is an epidemiologic investigation, and then also a laboratory study to do typing or fingerprinting of the bacteria that are identified in patients from their clinical specimens, and then also in the water samples that are tested to figure out where the actual source is.


    So not until those tests will we figure out whether this particular outbreak has been caused by those towers or the bacteria that is found elsewhere in the environment, as you described?


    Well, I think the investigation so far, as I understand it, is really pointing towards the cooling towers, but it's an ongoing investigation.

    And so I know that there's been extensive evaluation and there's been remediation or correction of the concern that has been identified. But it's ongoing. So I think we need to make sure that the information is all pulled together. These lab tests turn out to be really important, and they will take a bit of time.


    All right, Dr. Anne Schuchat from the CDC, thanks so much for joining us.


    My pleasure.

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