Can you catch Legionnaires’ disease at home?

A fifth person has died in connection with an outbreak of Legionnaires’ disease on Manhattan‘s Upper East Side, New York City’s health department said, as officials continue to work to contain the spread of the illness.

The outbreak, which health officials have traced to contaminated cooling towers in the affluent neighborhood, has now left 82 people unwell. Eight remain hospitalized, while 56 have been discharged. Officials said on July 21 that no new cases had been diagnosed in six days, and no one had reported new symptoms in more than 10 days, though they cautioned the promising numbers could still change as the outbreak continues.

Newsweek reached out to New York State’s Department of Health for comment.

Despite the outbreak being concentrated in one part of Manhattan, Legionnaires’ spread within cooling towers has raised a question for people far from the Big Apple: can the same bacteria make you sick through everyday household fixtures, like your shower perhaps?

What Is Legionnaires’ Disease?

Tyler B. Evans, founder and CEO of Wellness Equity Alliance and former chief medical officer for New York City’s COVID-19 response, told Newsweek that Legionnaires’ disease is an illness caused by bacteria.

“It can cause mild symptoms like a fever, or serious problems like pneumonia, a lung infection that makes it hard to breathe,” he said.

Evans explained that the disease begins when bacteria grow in warm water systems and get released into the air. He said the bacteria can develop in cooling towers used by large air-conditioning systems, water pipes connected to showers and sinks, and hot tubs and large building plumbing systems.

“People get sick when they breathe in tiny water droplets that contain the bacteria,” Evans said. “It does not spread from person to person.”

The Centers for Disease Control and Prevention says that while the disease is treatable it kills about 10 percent of patients.

What Causes Legionnaires’ Disease?

As Evans explained, Legionella can grow in cooling towers used by air-conditioning systems, water pipes connected to showers and sinks, hot tubs, splash pads, decorative fountains and building plumbing systems too.

That distinction matters for at-home risk away from Manhattan, as infection requires breathing in a fine mist of contaminated water, not simply touching or drinking it.

Showers and Water Heaters

The bacteria naturally exist in freshwater sources like lakes and rivers, but people typically become infected through man-made water systems where it can grow and spread in tiny water droplets, as seen in New York.

By this logic, household plumbing can theoretically harbor the bacteria, particularly when water sits unused for long stretches at the wrong temperature, or when water heaters are set at low temperatures that allow bacteria to survive.

Public health guidance generally advises keeping water heater temperatures high enough to limit bacterial growth, while balancing the risk of scalding, and running taps and shower heads periodically in homes that are vacant for extended periods.

Hot Tubs

Hot tubs are considered one of the more established non-cooling-tower sources of Legionella exposure, since they combine warm water with the kind of aerosol-generating bubbles that can carry bacteria into the air. Regular disinfection and proper maintenance are the standard safeguards, though no cases associated with hot tub use are on health officials’ radars at present.

Humidifiers and CPAP Machines

Cool-mist humidifiers and central humidification systems can pose a risk if they are not cleaned according to manufacturer instructions, since standing water in a reservoir can allow bacteria to multiply before being dispersed as mist.

CPAP machines carry a similar theoretical concern, which is why manufacturers often recommend routine cleaning schedules.

Contaminated tap water is not considered a major documented source of Legionnaires’ cases tied to CPAP use, but following cleaning guidance remains a basic precaution even without the disease making headlines.

Garden Hoses

Hoses are generally considered a very low risk.

Some experts note that water left sitting in a hose in the sun could theoretically warm enough to allow limited bacterial growth, but hoses are not a recognized source of outbreaks the way cooling towers are.

Can You Get It From Drinking Water?

Legionnaires’ disease is contracted by inhaling contaminated droplets, not by swallowing water.

Drinking water from an affected system is not considered a route of infection. In fact, New York City Mayor Zohran Mamdani said on July 6 that the city’s tap water is safe following the outbreak.

Who Is Most Vulnerable

Evans said the disease disproportionately harms communities that have long been underserved, and who perhaps cannot maintain the facilities they use as easily as better off residents.

“Like many disease outbreaks, Legionnaires’ disease often affects communities that have been underserved for a long time,” he said, adding that these areas are more likely to have “ongoing health problems, such as asthma or other lung conditions,” which can worsen outcomes.

He added that age and certain health conditions raise the risk of severe illness after exposure, rather than the risk of exposure itself.

“Age and certain health problems, such as lung disease, diabetes, kidney disease, a weakened immune system, or smoking now or in the past, make people more likely to become seriously ill once exposed,” he said.

Prevention Comes Down to Maintenance

The most effective way to reduce the risk of Legionnaires’ disease is through a comprehensive water management program that includes routine monitoring, proper water treatment, regular maintenance, and prompt corrective action whenever conditions indicate an increased risk.

Evans put it more bluntly: “You cannot vaccinate against Legionnaires’. You maintain against it. Clean, well-managed water systems prevent this disease.”

Dr. Suraj Saggar, the chief of infectious disease at Holy Name Medical Center in Teaneck in New Jersey, agrees. He told Newsweek that routine water testing and maintenance are incredibly important.

“Hospitals, for example, regularly test their water systems for Legionella as part of standard infection prevention practices,” he said. “Building owners should also ensure that cooling towers, plumbing systems, and other water sources are properly maintained and, when appropriate, tested.

“Cases tend to increase during the summer months, when cooling systems and other water-based recreational facilities are used more frequently. Older buildings with aging plumbing systems can also be at higher risk if water systems aren’t properly maintained, but as for prevention, people don’t need to avoid air conditioning, water parks, or splash pads altogether.”

Contact Newsweek editors on this story: Kara Dolman and Emma Lee-Sang