Cases of Legionnaires’ Disease, a Bacterial Lung Infection Spread by Water, are Growing

It most often affects older adults with weakened immune systems

There have been several outbreaks this year of a severe form of pneumonia first identified four decades ago when it made more than 200 people sick at the American Legion Convention in Philadelphia.

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The illness those Legionnaires contracted would go on to be named Legionnaires’ disease, and they got it from harmful bacteria that had been passed through the hotel’s air conditioning system.

Legionnaires’ disease is caused by strains of a bacteria called Legionella. The bacteria can live in fresh water sources but thrive in water that is warm and still or that hasn’t been properly disinfected. Outbreaks of the disease are commonly associated with large-scale water systems in hotels, hospitals, long-term care facilities and cruise ships, according to the Centers for Disease Control and Prevention.

The infection can cause severe illness. But that doesn’t necessarily mean you need to start skipping the hotel hot tub or not power up the air conditioning when it’s 90 degrees outside. Legionnaires’ disease occurs most often in a certain set of at-risk people and is relatively uncommon compared to other forms of infectious diseases.

How is Legionnaires’ disease spread?

You don’t get Legionnaire’s disease by coming in contact with someone who has it or drinking contaminated water (though you can get it by aspirating water that’s contaminated – or, having it go “down the wrong pipe”). Rather, you get it by inhaling airborne droplets of water that are contaminated with Legionella. These droplets can come from hot tubs, showers, faucets, humidifiers, air conditioning units or other water features.

Most healthy people who are exposed to the bacteria won’t develop Legionnaires’ disease, says Elliot Dasenbrook, MD, a pulmonary medicine specialist. It more often sickens people over 50 and those whose immune systems or lungs are weakened, such as people with cancer or diabetes or someone who’s had an organ transplant, he says.

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Recent outbreaks in the U.S. have occurred at places where seniors or people who are sick might frequently be, like hospitals, long-term care facilities and churches.

“The hard part is that once an outbreak has been identified, Legionella can be difficult to detect, and the bacteria can sometimes survive efforts to kill it,” Dr. Dasenbrook explains.

The number of cases of Legionnaire’s disease reported in the U.S. nearly doubled between 2012 and 2017, according to the CDC. It’s not clear exactly why the number of cases is on the rise, but an aging population that’s more susceptible to getting it is probably a factor, Dr. Dasenbrook says.

The total number of Legionnaires’ disease cases reported in the U.S. in 2017 was 7,458. About 1 million people seek hospital care for all forms of pneumonia each year.

Is it Legionnaires?

Legionnaires’ disease can be tough to recognize because symptoms are nearly identical to symptoms of other kinds of pneumonia, including:

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  • Cough
  • Shortness of breath
  • Fever

“We almost always check for Legionella in anyone that’s hospitalized with pneumonia that’s really sick, just because there aren’t really any telltale signs,” Dr. Dasenbrook says. “One hint that it may be Legionella is if patients have a lot of GI symptoms with their pneumonia – nausea, vomiting, diarrhea or a low sodium level, or if they don’t respond to the usual antibiotics.”

Can I prevent it?

Unfortunately, you can’t see Legionella with the naked eye, so there’s no way to know if you’re being exposed to it. There’s also no vaccine to prevent Legionnaires’ disease.

The key to prevention is better maintenance of water systems, the CDC says.

Most cases can be treated successfully with an antibiotic. Sometimes, though, it can lead to lung failure or other complications. Because of these potentially serious complications, many people who get Legionnaires’ disease need to be treated in a hospital.

Consult your physician right away if you develop cough, fever, shortness of breath and nausea, especially after a known exposure to the bacteria.

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