Legionella pneumophila is a bacterium usually found in small amounts in water in nature and humanmade water systems. In larger amounts, L. pneumophila can cause a severe pneumonia known as Legionnaires’ disease. Transmission occurs almost exclusively from the environment, such as when someone inhales contaminated aerosols from nearly any water source. Sources include showers, air conditioning cooling towers, and decorative water fountains. Person-to-person transmission is extremely rare. Although research has implicated some other, uncommon sources of contamination (e.g., supermarket mist machine and windshield washer fluid), transmission through flushing toilets has been suspected but not demonstrated.
Researchers now report two cases of Legionnaires’ disease in hospitalized immunocompromised patients hospitalized in the same room five months apart in France, potentially caused by L. pneumophila transmission through flushing contaminated toilets. Whole-genome sequencing analyses showed that clinical isolates from the patients and isolates from the room’s toilet were closely related genetically. Toilet contamination by L. pneumophila could pose a risk for exposure through flushing. However, laboratory-based studies can confirm whether flushing toilets can indeed generate and spread contaminated droplets through the air.
Reference Couturier J, et al. Transmission of Legionnaires’ Disease through Toilet Flushing. Emerging Infectious Diseases. Vol. 26, No. 7. 2020. Article ID: 19-0941.