UK Hospital Water Supply Linked to 40 Mycobacterium Abscessus Infections Over Six Years

Between May 2019 and June 2026, 40 patients at the Royal Papworth Hospital in Cambridge, England, contracted bacterial infections linked directly to the facility’s internal water supply, according to an investigation published by the UK Health Security Agency and research teams in Clinical Infectious Diseases.

The outbreak centers on Mycobacterium abscessus, a non-tuberculous mycobacterium found naturally in water, soil, and dust. While the organism typically poses no threat to healthy individuals, it presents severe pulmonary risks for immunocompromised patients or those with underlying lung conditions. As a specialist heart and lung hospital managing complex respiratory treatments and organ transplants, Royal Papworth Hospital regularly treats vulnerable patient populations facing heightened susceptibility to waterborne pathogens.

The Timeline of Contamination and Discovery

The facility relocated to a new building in May 2019. By August of that same year, hospital clinicians detected Mycobacterium abscessus in two separate lung transplant recipients, prompting an immediate internal investigation. Subsequent environmental testing of the hospital’s water systems in November 2019 confirmed the presence of the exact same bacterial strain within the plumbing infrastructure.

Researchers conducted a genomic analysis comparing patient clinical samples against environmental specimens collected from hospital water and equipment between 2019 and 2025. By matching the genetic profiles of the waterborne bacteria with those isolated from patients, investigators attributed 40 distinct cases to the hospital water source.

The 40 affected individuals comprised 11 lung transplant recipients, 11 patients diagnosed with cystic fibrosis, 14 patients suffering from non-cystic fibrosis bronchiectasis, and 4 individuals under other clinical categories. Out of the 40 patients carrying the bacteria, 19 developed formal diagnoses of non-tuberculous mycobacterial pulmonary disease. Ian Smith, a medical professional at Royal Papworth Hospital, noted that clinical manifestations vary widely, with some patients displaying symptoms immediately, others developing signs years later, and some remaining entirely asymptomatic.

Infrastructure Remediations and Persistent Challenges

Tragic outcomes underscored the severity of the contamination. Two female lung transplant recipients died following their infections. A coroner’s report issued in 2022 determined that the hospital’s water supply served as the source of the bacteria, concluding that the Mycobacterium abscessus infections directly contributed to their deaths.

In response to the crisis, hospital administrators deployed a multi-layered engineering defense. Teams installed specialized filters on washbasin taps and showerheads, supplied bottled drinking water to high-risk patients, and integrated both an ultraviolet irradiation system and a hydrogen peroxide dosing apparatus into the main water supply to suppress bacterial proliferation.

These mitigation efforts yielded a measurable decline in incidence rates, dropping new related cases from an annual average of 12.8 down to 2.2. Following operational adjustments to plumbing flushing protocols in June 2025, zero new cases were identified through the end of the study period in June 2026.

Environmental audits conducted by the UK Health Security Agency between 2022 and 2025 revealed that while point-of-use filters successfully barred the bacteria from treated tap water, Mycobacterium abscessus persisted within facility infrastructure. Investigators detected the organism in wastewater drains, toilet water, and drain traps. Furthermore, May 2025 testing recovered the bacteria across all four tested toilet water samples and all three air samples collected immediately after flushing toilets. Researchers emphasized that while engineering controls successfully suppressed clinical transmission, completely eradicating the organism from complex hospital plumbing remains an ongoing challenge for facilities housing vulnerable respiratory patients.