Legionnaires' disease outbreak in NYC kills 5: How dangerous Legionella bacteria multiply in ACs and cooling towers, symptoms, prevention and treatment explained

New York is currently battling the outbreak of Legionnaires disease due to which five people have died, reports news agency AP. The health officials have confirmed that more than 66 people have fallen ill over the past month due to the outbreak.

The New York City Health Department announced Tuesday that Legionella bacteria have been detected in 34 cooling towers across 33 buildings, all of which are now being cleaned and disinfected. Officials are still investigating to determine the exact source of the outbreak.

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According to the health department, no new patients have shown symptoms of Legionnaires disease in the past ten days.

According to health officials, eight patients remain hospitalized, while 56 others have been treated and discharged. In total, the city is cleaning and disinfecting 82 cooling towers in 80 buildings in an effort to eliminate any remaining contamination.

What Is Legionnaires Disease?

Legionnaires' disease is a serious type of pneumonia caused by Legionella bacteria. The bacteria naturally exist in freshwater but become dangerous when they multiply in warm, man-made water systems such as cooling towers, air-conditioning systems, hot tubs, decorative fountains and large plumbing systems.

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The illness can be severe but is treatable with antibiotics, especially when diagnosed early. According to the US Centers for Disease Control and Prevention (CDC), about 1 in 10 people diagnosed with Legionnaires' disease die from the infection, although outcomes improve significantly with prompt treatment.

Unlike the flu or COVID-19, Legionnaires' disease does not spread from person to person.

Where Is the New York City Outbreak?

The outbreak is centered in Manhattan's Upper East Side, where inspectors have found traces of Legionella bacteria in multiple cooling towers.

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Health officials said the bacteria have been detected in cooling equipment at several buildings, including luxury apartment complexes, private schools and well-known cultural institutions.

The Guggenheim Museum said in a statement that an outside contractor tests and treats its cooling tower every month as part of its maintenance program.

Officials have not yet identified which cooling tower or building first triggered the outbreak.

Symptoms of Legionnaires Disease

Symptoms usually develop two to 10 days after exposure, although they can sometimes take longer.

Common symptoms include:

• High fever
• Chills
• Cough
• Shortness of breath
• Chest pain
• Muscle aches
• Headache
• Fatigue
• Nausea, vomiting or diarrhea
• Confusion, particularly in older adults

Doctors advise anyone who develops pneumonia-like symptoms after being in an affected area to seek medical care promptly. Early diagnosis and antibiotic treatment greatly improve recovery.

How does Legionnaires' Disease Spread?

People become infected by breathing in tiny water droplets (mist) that contain Legionella bacteria.

Common sources include:

Cooling towers on large buildings
Hot tubs and spas
Decorative fountains
Large plumbing systems
Industrial water systems

The disease does not spread through drinking water in most cases because stomach acid usually destroys the bacteria. It also does not spread from one person to another.

Are you at risk?

While anyone can develop Legionnaires' disease, some people face a much higher risk of severe illness.

Those at greater risk include:

• Adults aged 50 years and older
• Current or former smokers
• People with chronic lung disease
• Individuals with weakened immune systems
• People with cancer, diabetes or kidney disease
• Organ transplant recipients
• Those taking medications that suppress the immune system

Healthy people can become infected, but serious illness is much less common.

How Is Legionnaires' Disease Treated?

Legionnaires' disease is treated with antibiotics, and many patients require hospitalization for oxygen therapy or other supportive care if symptoms become severe.

Doctors stress that early treatment is critical, as prompt antibiotic therapy can significantly reduce the risk of complications and death. Most patients recover fully, although recovery can take several weeks depending on the severity of the infection.

The outbreak comes despite New York City's strengthened regulations on cooling tower inspections introduced earlier this year.

Following a deadly Harlem outbreak last year that killed seven people, city leaders approved funding to expand the Health Department's Legionella inspection team. Officials said the department currently has 35 inspectors, with 14 more undergoing training and plans to fill seven remaining positions.

The agency added that it completed nearly 1,600 cooling tower inspections during the first six months of the year, a 35% increase compared with the same period in 2025.

(With AP inputs)