Hot tubs found in cruise ships are linked to outbreaks of Legionnaires’ disease, according to the U.S. Centers for Disease Control and Prevention.
From winter 2022 to spring 2024, eight confirmed cases were reported on ‘cruise ship A’. It was the largest cruise-related outbreak of Legionnaires’ disease since 2008.
Following an investigation, the CDC concluded that the infections likely spread in the ships’ hot tubs.
Between January and June 2024, four additional cases of Legionnares’ disease were confirmed on another cruise ship, ‘cruise ship B’, with the hot tubs being the source of the infection.
The CDC said in a report that private hot tubs, such as those found in cruise ships, are not subject to the same strict operating requirements as public hot tubs.
More specifically, they are not required to have automated pH monitoring or continuous disinfectant dosing. The only requirement is that they must be drained, shock-chlorinated, and refilled with water every week.
As such, they are much more likely to harbor bacteria such as Legionella.
For example, the chlorine levels may not be high enough to suppress bacterial growth. The bacteria can also form biofilms on hidden surfaces and pipes, which makes them difficult to spot.
What Is Legionnaires’ Disease?
Legionnaires’ disease is a serious type of pneumonia that’s caused by the Legionella bacteria. Unlike other types of bacteria, it thrives in warm water, which makes hot tubs favorable for their growth. The bacteria then enters the body through inhaled water droplets when the hot tub releases mists or fine sprays.
Aside from hot tubs, the bacteria can also thrive in air humidifiers or air conditionings. However, the disease cannot be transmitted from person to person.
Legionnaires’ disease is named after an outbreak that happened at an American Legion convention in 1976. Following the event, many individuals started to become ill with an atypical form of pneumonia. Scientists later identified a bacteria – later named Legionella pneumophila – as the cause.
People who are infected with the bacteria are typically treated with antibiotic and oxygen therapy. Even with medical intervention, however, up to ten percent of those infected can die.
According to the CDC report, six people from cruise ship A and four people from cruise ship B required hospitalization.
Older people, especially those with existing health conditions, are also at a higher risk for complications and serious infection. For example, they may develop septic shock, respiratory failure, or acute kidney failure, all of which can be potentially life threatening.
Symptoms of Legionnare’s Disease
Most people will develop symptoms a few days after being exposed to the bacteria. Initial symptoms include muscle aches, headache, and high fever.
As the disease progresses, they may develop other signs such as chest pain, cough, shortness of breath, confusion, nausea, or vomiting.
