What We Know About the Legionnaires’ Disease Outbreak in New York
An outbreak of Legionnaires’ disease in Central Harlem has sickened at least 67 people and caused three deaths since the outbreak was identified on July 25, according to the NYC Health Department. Per the CDC, the disease, a type of pneumonia that presents with flulike symptoms, is caused by bacteria that often spreads through manmade water systems and standing water. Here’s what we know.
What is Legionnaires’ disease?
Legionnaires’ is caused by a bacteria called Legionella. There are several strains of it, some of which cause Pontiac fever (a related but less severe version of Legionnaire’s) or don’t cause symptoms at all. The strain that causes Legionnaires’ disease is especially dangerous because of the way it infects the body by invading human cells, using their nutrients to grow and spread.
“Legionella lives in pretty much any water system,” says Dr. Michael Phillips, the chief epidemiologist at NYU Langone Health, and it is often found on the inside surface of pipes and water tanks. Dr. Bernard Camins, the medical director for infection prevention at the Mount Sinai health system, says the bacteria often spreads through infected water supplies like a building’s boiler, a city water tank, or cooling towers, the mechanical systems that large buildings use to force hot air out. After a severe 2015 outbreak in the Bronx that killed 13 people, New York City passed a local law requiring the owners of buildings with cooling towers to register, maintain, and test their systems, which is typically done by adding chlorine. That policy may not have prevented this outbreak, but increased testing is likely the reason it was caught early.
For the most part, Legionella is present in water systems at fairly low levels, but it becomes more common in warmer months when water temperatures increase, since the bacteria proliferate in warm, shallow water. Though the numbers we’re seeing in the current outbreak are concerning, Dr. Camins says physicians get warnings about the disease from the Department of Health ahead of every summer. “It will continue to happen annually,” he explains. “In this situation, we’re more concerned because multiple people are being affected; it’s usually just single patients, so we definitely know that a common source is affecting a lot more people than we would like.”
What’s causing the current outbreak?
The New York Times reports that the bacteria has been detected in 11 cooling towers in Central Harlem in the past few days, which are most likely spreading the disease via water vapor. In large buildings, cooling towers stop a building from getting too hot by expelling the heat into the atmosphere via evaporation. “Many of these have fans on top of them and they’re basically blowing these aerosols,” explains Dr. Phillips. The problem is, those aerosols can contain Legionella. That also means the disease does not spread from person to person. According to Dr. Phillips, “You don’t generate enough aerosol, as a person who’s sick, to make somebody else sick.”
What are the symptoms?
In short, look out for all the usual flulike symptoms that come with pneumonia and other respiratory illnesses: A dry cough, shortness of breath, and fever. Dr. Camins says that with Legionaires’ disease specifically, you’re more likely to experience nausea and other GI issues.
Dr. Phillips says that because of the unique way it attacks the cells, Legionnaires’ tends to be a particularly severe form of pneumonia. That’s why, he says, so many people end up hospitalized, and the mortality rate can be as high as 10 percent during a given outbreak.
Who’s most at risk?
Since the bacteria specifically spreads from water source to person, outbreaks like this one are pretty strictly geographic, says Dr. Phillips. The department of health has listed five Zip Codes in Central Harlem that are currently affected: 10027, 10030, 10035, 10037, and 10039. But beyond that, the patients with the highest risk are those who are immunocompromised or have other comorbidities. Dr. Camins says smokers, people with lung cancer or lung disease, or over the age of 50 are at a higher risk.
Still, Dr. Phillips recommends that “anybody, particularly in the Zip Codes of concern,” get checked out if they’re experiencing “fever, cough, [or] feeling like they have the flu.”
Dr. Phillips also says that certain medications can affect immunity, including those that treat inflammatory bowel disease, rheumatoid arthritis, and cancer. “There’s many more patients taking those drugs now than even there was ten years ago,” he explains. “That’s a population that could get Legionnaires’ more severely and certainly should be on guard for symptoms.”
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