Toilet Flushes May Spread Legionnaires’ Disease

November 29, 2020

Legionnaires’ disease may be spread by flushing toilets, which releases invisible “plumes” of contaminated water into the air, according to a new report.

The report, published Wednesday (June 10) in the journal Emerging Infectious Diseases, describes the likely case of two patients at a French hospital who contracted Legionnaires’ disease by inhaling contaminated toilet water that was aerosolized during the flush. The two patients lived in the same hospital, but five months apart.

Although the researchers suspected that the toilet plume could transmit Legionnaires’ disease, this is the first time that genetic analysis has linked a patient’s infection to contaminated toilet water, “strongly suggesting that toilet water is the source of infection.” Dr. Jeanne Couturier, lead author of the study and a medical biologist at St. Antoine’s Hospital in Paris, told Live Science.

According to the Centers for Disease Control and Prevention (CDC), Legionnaires’ disease is a serious lung infection, or pneumonia, caused by Legionella bacteria. The bacteria lives in watery environments and becomes a health problem when it grows and spreads in building water systems such as cooling towers, hot tubs, shower heads, sink faucets and decorative fountains. People become infected when they breathe in droplets of water (in steam or mist) that contain bacteria in the air. The disease is not usually spread from person to person.

Many people exposed to Legionella don’t get sick, but those at increased risk of contracting the disease include the elderly and people with weakened immune systems or chronic lung disease, according to the CDC.

Two patients in the new report have weakened immune systems. One was an 18-year-old who underwent a bone marrow transplant and was taking immunosuppressive medications before being hospitalized in December 2015 for transplant-related complications. The other was a 51-year-old man who was hospitalized in May 2016 for treatment of Hodgkin’s lymphoma, a cancer of the immune system.

Both patients developed Legionnaires’ disease during their hospitalization or shortly after discharge, so their infections were determined to be likely healthcare-related. Both patients recovered after receiving antibiotics.

Investigation of the source of the infection revealed that Legionella was present in the toilet water in the room, but not in the shower or sink of the room.

Genetic analysis revealed that the strain of bacteria in the toilet water was the same or closely related to the strain that infected the patient. No other potential sources of infection were found.

To see if this was a widespread problem, the authors said, the researchers took samples from 29 toilets in five different hospital buildings, but none of the samples tested positive for Legionella, suggesting that this type of contamination – and route of transmission – is rare.

The contaminated toilets were disinfected daily with bleach, which proved effective in preventing the growth of Legionella – and no more samples from the toilets tested positive over the next year and a half.

Couturier said another way to prevent the potential spread of Legionella through the aerosols created when flushing is to close the lid before flushing.

“It seems important to educate patients to close the toilet lid before flushing, especially immunosuppressed patients or those with comorbidities who are at greater risk for Legionnaires’ disease,” Couturier said.

Couturier said the findings also suggest that teams investigating cases of Legionnaires’ disease in health care facilities should consider flushing the toilet as a possible transmission route and test samples of toilet water for contamination if no other more common sources of Legionella contamination (such as showers and faucets) are found.

It is important to note that the report could not definitively prove that toilet water was the source of infection for the patient. To prove that flushing a toilet can transmit Legionnaires’ disease, researchers would need to conduct experimental studies in a controlled laboratory setting. For example, researchers could contaminate toilet water with Legionella bacteria, flush the toilet, and then collect samples from the air and nearby surfaces to test whether those samples contain the bacteria, Couturier said.