Legionnaires’ Disease: What You Need to Know

A new Legionnaires' disease cluster has recently been identified in the Upper East Side, with at least 18 cases identified by city officials. Last year, more than 60 cases of Legionnaires’ disease were diagnosed in and around Central Harlem, with at least three deaths reported. 

Daniel Griffin, MD, PhD, an infectious disease specialist at Columbia’s Vagelos College of Physicians and Surgeons, explains the symptoms of Legionnaires’ disease, whether it’s contagious, and how to reduce your risk.

What is Legionnaires’ disease, and what causes it?

Legionnaire’s disease is a type of pneumonia caused by the bacteria Legionella. While these bacteria can cause other problems (such as skin infections, heart infections, meningitis, and kidney failure), when we talk about Legionnaires’ disease, we’re talking about a type of pneumonia.

What are the most common symptoms of Legionnaires’ disease?

Legionnaires’ disease looks a lot like pneumonia caused by other bacteria or viruses. For example, the lung exam and chest X-ray of someone with Legionnaires’ disease may be indistinguishable from other types of pneumonia.

People with the disease may have fever, cough, and trouble breathing. They often report feeling poorly.

If someone has these symptoms, what should they do?

If you have any of these symptoms, you should see your doctor. If they suspect Legionnaires’ disease based on certain features, they will likely prescribe an antibiotic. They will make sure you get the treatment that is right for you.

How does someone typically get Legionnaires’ disease? Why do city officials and the news media keep mentioning cooling towers?

Legionella bacteria live inside the tiny organisms (paramecia, amoebas) that are often present in unfiltered water. If this contaminated water becomes airborne, as a very fine spray or an aerosol, people can inhale it. Hot tubs with bubbling warm water are known to produce cases of Legionnaires’ disease.

In New York, officials and the news media have focused on cooling towers. Buildings in the city use cooling towers on their roofs as part of their air-conditioning systems. These towers, if not properly cleaned and maintained, can throw off contaminated water that passersby can inhale. That’s the most likely explanation of the recent Legionnaires’ disease cluster.

Is Legionnaires’ disease contagious? Can someone get it from another person?

No. People with Legionnaires’ disease are not contagious. People get Legionnaires’ disease by breathing in water vapor contaminated with the Legionella bacteria.

Who is most at risk?

Most healthy people exposed to Legionella will either not get sick or have a mild illness that resolves on its own. That said, certain individuals are at higher risk and can become seriously ill and even die. These include older individuals (over age 65), people with chronic diseases, and people with compromised immune systems.

What precautions can people take to lower their risk of Legionnaires’ disease?

The best way for individuals to stay safe is to be aware of their environment and use common sense. For example, when walking on the sidewalk, steer clear of window air conditioners and the moisture they throw off. And skip the hotel hot tub. Take a hot shower instead.

And for those who have air conditioners, fountains, misters, or humidifiers, be sure to clean and disinfect them periodically. That way, we can all enjoy their benefits without sickening anyone.