CDC reports link between Legionnaires' disease outbreak and cruise ship hot tubs

According to reports, U.S. cruise ship hot tubs have been linked to recent outbreaks of Legionnaires’ disease.

According to a report from the Centers for Disease Control and Prevention (CDC), multiple infections were traced back to private outdoor hot tubs on the balconies of two cruise ships between November 2022 and June 2024.

The CDC stated in a report that private balcony hot tubs were the probable cause of exposure in two outbreaks of Legionnaires’ disease among cruise ship passengers, based on epidemiologic, environmental, and laboratory evidence.

Warm temperatures in hot tubs can promote the growth of Legionella bacteria, as stated by Waleed Javaid, MD, an epidemiologist and director of infection prevention and control at Mount Sinai Downtown in New York.

Javaid, not linked to the CDC report, informed Planet Chronicle Digital that the aerosolization and bubbling of the substance facilitate the inhalation of bacteria, which is the primary mode of infection.

What to know about Legionnaires’ disease

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

According to Dr. Andrew Handel, a pediatric infectious diseases expert at Stony Brook Children's Hospital on Long Island, New York, the bacteria can thrive in any location where water remains stagnant for an extended period.

Consuming or inhaling water droplets contaminated with Legionella may lead to illness.

The CDC states that while human transmission of the disease is possible in rare instances, it is not typically spread from person to person.

Pneumonia can be severe in older people and those with weakened immune systems due to infections, Handel cautioned.

Handel stated that Legionella infections can cause symptoms similar to other types of pneumonia, including fever, coughing, difficulty breathing, shortness of breath, and chest pain.

The CDC noted that some patients may experience nausea, diarrhea, and confusion in addition to the flu.

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

In severe cases of infection, hospitalization may be necessary for breathing support and IV hydration, and antibiotics are typically used to treat the condition.

The CDC reports that approximately 10% of individuals who contract Legionnaires' disease may die from complications, and the mortality rate increases to 25% for those who develop the condition while staying in a healthcare facility.

Around 10% of people who contract Legionnaires’ disease will die from complications, according to the CDC.

It is crucial to seek medical attention immediately if someone suspects exposure to Legionella bacteria, as prompt intervention may enhance the likelihood of a full recovery, according to infectious disease experts.

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Watch out for symptoms such as cough, shortness of breath, fever, muscle aches, and headaches if you have recently used a hot tub and are concerned about Legionnaires' disease, Javaid advised. These symptoms may appear between two and 14 days after exposure.

If you notice these signs, especially if you fall into a vulnerable category, act quickly, he advised.

The CDC’s findings

According to the CDC report, two cruise ships reported a total of twelve cases of Legionnaires’ disease among their passengers.

Ten out of the twelve sickened individuals were hospitalized, with no reported deaths.

The report did not specify the names of the cruise ship companies, only referring to them as cruise ships A and B.

The hot tubs were found to be promoting the growth of Legionella by the CDC.

The report stated that the conditions included water running at temperatures between 77 and 113 degrees Fahrenheit for several days without draining and without any residual disinfectant.

The report pointed out that people could have been exposed to aerosols without using the hot tubs, which were situated near outdoor areas.

Public hot tubs on cruise ships are subject to "more stringent operating requirements" than private hot tubs, the agency noted.

Despite following the current CDC guidelines for operating and maintaining private hot tubs, Legionella growth still occurred.

The CDC report states that the cruise ships collaborated with the investigation and took measures to reduce Legionella growth.

The CDC advises hot tub owners and operators to follow safe procedures for operation and maintenance to prevent exposure to Legionella and reduce the risk of bacterial growth and transmission.

The CDC emphasized the importance of an automatic disinfectant dosing system in preventing growth, stating that handfeeding disinfectant is not as effective.

Enjoying hot tubs safely

The experts provided guidance on how to reduce exposure to bacteria while using hot tubs.

Javaid advised people to stay informed but not alarmed when they are worried.

"It's important to monitor the cleanliness of public hot tubs, especially if you belong to a high-risk group."

Javaid advised that it is reasonable for cruise-goers to inquire about the maintenance and disinfection of hot tubs, and to avoid those that have an unusual odor or appear neglected.

"The hot, stagnant water has the potential to transmit a number of harmful bacteria and viruses that can cause severe illness in high-risk individuals."

Legionnaires’ disease poses a higher risk to certain populations, such as individuals of advanced age, smokers, people with chronic lung conditions, and immunocompromised people, according to the expert.

Handel advised that hot tub owners should adhere to health recommendations for maintaining clean water and equipment.

Handel advised caution for older or immunocompromised individuals before using hot tubs, as while they can be safe when properly maintained, it's best to consult with a medical provider first.

"Stagnant water can harbor harmful bacteria and viruses, posing a severe health risk to high-risk individuals."

The CDC provided the following general recommendations to Planet Chronicle Digital.

"To prevent waterborne germs such as Legionella at home, it is recommended to flush faucets and showerheads after not using them or water pressure drops, clean and maintain devices that use water (e.g. humidifiers, nasal rinses, showerhead and faucet aerators, water filters), and check and flush water heaters regularly."

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Although Handel acknowledged that there have been some advancements in water treatment and surveillance, the incidence of Legionella infections has decreased.

Currently, there are no vaccines for Legionnaires’ disease.

Four popular cruise lines were contacted by Planet Chronicle Digital for information on their hot tub maintenance procedures, but no response was received before publication.

Planet Chronicle’ Melissa Rudy contributed reporting.