Deadly Legionnaires' disease outbreak sparks concern in major US city: Know the symptoms

Amid warnings of a Legionnaires' disease outbreak on Manhattan's Upper East Side, health experts say that early recognition of symptoms can mean the difference between a quick recovery and life-threatening complications, especially for high-risk groups.

New York City health officials are urging anyone who has visited the east side of Central Park or Manhattan's Upper East Side since late June to watch for symptoms.

As of July 6, the New York City Health Department had confirmed 23 cases and 17 hospitalizations associated with the respiratory infection. No deaths have been reported.

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Officials are investigating contaminated cooling towers as the likely source. They have emphasized that the illness is not spread person-to-person and is not linked to the city's drinking water.

"Legionnaires’ disease is deadly but can be effectively treated if diagnosed early," said NYC Health Commissioner Dr. Alister Martin in a press release. "New Yorkers at higher risk, including anyone who is 50 and older, those who smoke or people with chronic lung conditions should be especially mindful of their symptoms and seek care as soon as symptoms begin."

Legionnaires’ disease is a type of pneumonia caused by Legionella bacteria.

The bacteria is usually found in lakes, streams and other freshwater environments, but can grow in any area where water sits for a long time, according to the CDC.

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That can include shower heads, sink faucets, hot tubs, water features/fountains, plumbing systems and other water systems.

When people swallow or breathe in droplets of water that contain Legionella, they can potentially become ill.

Although human transmission is possible in rare cases, the disease is not typically transmitted among people, per the Centers for Disease Control and Prevention.

Infections can lead to severe pneumonia in older people and those with compromised immune systems, according to Dr. Andrew Handel, a pediatric infectious diseases expert at Stony Brook Children's Hospital on Long Island, New York.

Symptoms of Legionnaires’ disease usually show up between two and 14 days after exposure.

"Legionella infections cause symptoms that are similar to other forms of pneumonia — fever, coughing, difficulty breathing, shortness of breath and chest pain," Handel previously told Fox News Digital.

The signs are similar to other types of pneumonia, and include the following:

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Some patients may also experience nausea, diarrhea and confusion, the CDC noted.

A medical professional can diagnose the infection with laboratory tests and chest X-rays.

The condition is typically treated with antibiotics. In cases of severe infection, hospitalization may be required for breathing support and IV hydration.

Around 10% of people who contract Legionnaires’ disease will die from those complications — and the mortality risk rises to 25% for those who get Legionnaires’ while staying in a healthcare facility, according to the CDC.

"Treatment needs to be early and aggressive," Dr. Nathan Goodyear, an Arizona-based integrative medicine expert, previously told Fox News Digital. "Legionella infection is an intracellular infection that requires antibiotic treatment."

Antibiotics that are appropriate for Legionella infection include Levofloxacin and Azithromycin. 

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"Therapy can be prescribed orally in healthy individuals … but intravenous antibiotics often prove to be the initial option for treatment secondary to the pathogenicity of the disease," Goodyear said.

Currently, there are no vaccines for Legionnaires’ disease. 

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The best strategy to prevent infection is to reduce the growth and spread of the Legionella bacteria. The CDC recommends that building owners and managers use a water management program to reduce the risk.

To prevent serious illness from Legionnaires’, Goodyear recommends that all smokers kick the habit, and also emphasizes the need to "aggressively support" chronic pulmonary disease.

"Increasing immune support (vitamin D3, vitamin C, Zinc) is required to counter the immune dysfunction associated with advancing age."

Obesity is another foundational risk factor for all chronic inflammatory diseases, the doctor added.