What Is Legionnaires’ Disease and How Can I Protect Myself?

Nearly one out of every 10 people who gets sick with Legionnaires’ dies because of complications from the illness. Here’s what to know about prevention, detection and treatment.

Health departments in the United States report nearly 10,000 cases of Legionnaires’ disease each year.
Credit...Francis Chandler/CDC via AP Images

Last week, the New York State Department of Health announced that it was investigating eight possible cases of Legionnaires’ disease that had occurred between June and September at the Amsterdam Nursing Home in Manhattan’s Morningside Heights neighborhood. Four of the eight people who might have been infected have died. Earlier this month, city officials also found evidence of the bacteria that causes Legionnaires’ at the Jacob Riis Houses in Manhattan’s East Village.

Health departments in the United States report nearly 10,000 cases of Legionnaires’ each year, but some experts believe the disease is still underreported because it can be difficult to distinguish from other lung infections. Nearly one out of every 10 people who gets sick with Legionnaires’ disease dies because of complications from the illness, according to the Centers for Disease Control and Prevention. The complications can include respiratory failure, heart inflammation and extensive muscle damage, all of which are more likely to occur in people ill enough to be admitted to the hospital.

Here’s what you should know about spotting symptoms, getting treatment and protecting yourself.

Legionnaires’ is caused by infection with Legionella bacteria, which is normally present in water but becomes potentially dangerous when it’s allowed to multiply in great numbers. The bacteria is common in freshwater sources such as lakes and streams, but it typically only becomes a health concern in man-made water systems, which provide a warm enough environment for the bacteria to grow and spread.

People can get infected if they breathe in small droplets of water containing Legionella while taking a shower, using a hot tub or simply going about their lives in a building with a large hot water tank, cooling tower or complex plumbing system, such as a hotel, hospital, long-term care facility, office building or school, said Dr. Elliott Dasenbrook, a respiratory disease specialist at the Cleveland Clinic. Some studies have also suggested that people who work in transportation get Legionnaires’ disease at twice the rate of non-transportation workers, possibly because the bacteria can proliferate in the windshield wiper fluid tank of a vehicle if it is diluted with plain water. Drivers may breathe in the contaminated mist when it is sprayed onto the windscreen.

“The mist that contains bacteria can be microscopic, so you can’t really see or feel it when you breathe,” Dr. Dasenbrook said. Most people do not get sick even if they are exposed to the bacteria, he added; older people and those with pre-existing conditions are the most likely to develop an infection.

If you do get infected, symptoms typically appear two to 14 days after an exposure. You may get a fever of 104 degrees or more, as well as chills, a cough, headache or overall weakness and fatigue. Unlike with other lung infections, people with Legionnaires’ may have additional gastrointestinal symptoms, such as nausea or diarrhea, Dr. Dasenbrook said. The disease gets progressively worse within the first week of developing symptoms and many patients end up in the hospital.

Sometimes Legionella bacteria can cause a less severe illness called Pontiac fever, in which the symptoms are limited to a fever and body aches. Those cases usually do not require treatment and resolve on their own in less than a week, according to the C.D.C.

Legionella infections are most common in the summer and early fall months, Dr. Dasenbrook said, when people living in high-rises are more likely to use their air-conditioners, requiring the use of the buildings’ cooling towers. Rates of Legionnaires’ infections are highest among older, Black and low-income people, who are more likely to live in poorly maintained housing with wider spread Legionella growth. (Central air in private houses and window air-conditioning units, as well as car units, do not use water to cool the air, so they do not typically carry a risk for Legionella growth.) Patients almost never spread bacteria to other people, Dr. Dasenbrook said, although researchers have noted a handful of rare exceptions.

You’re more vulnerable to an infection if you’re older than 50, have smoked cigarettes or have another long-term respiratory illness, such as chronic obstructive pulmonary disease or emphysema. People who have weakened immune systems — because of an organ transplant, cancer, diabetes or H.I.V. — and those who have recently stayed in a hotel, hospital or nursing home may also be at elevated risk for Legionnaires’ disease.

“That’s why it seems like every year you hear about a few outbreaks in nursing homes or long-term care facilities like that,” Dr. Dasenbrook said. “It’s usually those patients that have all of these different risk factors.”

If you have the above symptoms and notice any shortness of breath, reach out to a health care professional, Dr. Dasenbrook said. If you’re able to monitor your blood oxygen levels using a pulse oximeter and your oxygen levels start dropping below 95 percent, that is another reason to get evaluated.

Seek out medical care if you are experiencing severe gastrointestinal symptoms in addition to a cough and fever. You should talk to a doctor before the diarrhea or vomiting starts to make you dehydrated, Dr. Dasenbrook said. Be sure to mention if you have spent any nights away from home — at a hotel or in a hospital — in the past two weeks, as this can help your doctor home in on a potential case of Legionnaires’.

Your doctor will most likely order a chest X-ray to determine if you have a lung infection. People who are sick enough to go to an emergency room may also get blood work and urine tests done to determine the cause of infection. A combination of these tests and the patient’s history of travel and symptoms will most often be what’s needed to distinguish between Legionnaires’ and other types of infections.

Most cases require antibiotic treatment for five to 14 days, depending on the severity of illness and the patient’s underlying health. Even healthy people often need to receive care in a hospital and some may also require extra oxygen through a tube or mask. Patients may experience fatigue and muscle aches for several months after they go home.

You can reduce your risk of Legionnaires’ at home by regularly deep cleaning shower heads, faucets, hot tubs and humidifiers. There is no current guidance about how often individual households need to do this, but if you think you might be at risk, it’s fairly easy to kill Legionella bacteria: For your shower or faucet, start by detaching the shower head or the end piece of the faucet that contains a mesh screen disk. Scrub off the limescale and other residue. Then soak the piece in boiling water or a chemical solution to help kill the bacteria. For hot tubs, use chemicals specifically designed for disinfection, and for your humidifier, use either diluted bleach or a hydrogen peroxide solution. For your car, the C.D.C. recommends undiluted windshield cleaner fluid, which contains a mixture of antifreeze, solvent and detergents that are inhospitable to bacterial growth.

Most states require managers of large buildings that use cooling towers and water tanks to register them with the state. Managers also need to check regularly for Legionella, disinfect cooling towers within 24 hours if they have elevated levels of bacteria and notify the local health department and the public. In New York, these inspections must be conducted no less frequently than every 90 days.

If an infection is traced back to a specific facility, as with the recent cases in New York, water flow is typically restricted to protect residents. Those affected may have to switch to using bottled or boiled water for drinking and bathing until the building can finish disinfection.