Science1 publisher3 min readPublished
UKHSA traces 40 Mycobacterium abscessus infections to Royal Papworth's new water system
UKHSA researchers tie 40 Mycobacterium abscessus infections, two linked to deaths, to Royal Papworth Hospital's new water system between 2019 and 2025. The case shows a new building's plumbing can keep exposing transplant and cystic fibrosis patients for years after the taps are filtered.
The Scientist · Science desk
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What happened
- Both women who died had received double lung transplants at the newly relocated hospital, and a coroner's inquest concluded the infection contributed to each death.
- Of the 40 cases, 11 were lung transplant recipients, 11 had cystic fibrosis, 14 had non-cystic fibrosis bronchiectasis and 4 came from other patient groups.
- Swabs of hospital surfaces and medical equipment found no sign of the bacterium during the hospital's environmental sampling.
- A hydrogen peroxide dosing plant and a UV unit installed to kill the bacteria in the incoming water supply did not succeed.
- UKHSA sampling from 2022 to 2025 found no mycobacteria in filtered tap water, but patients were still at risk from drain traps and toilets.
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Why it matters
- exposure Filtering every tap still leaves immunocompromised patients reachable through drain traps and toilet flushes, so those outlets need controls of their own.
- constraint With dosing of the incoming supply ineffective, control at Royal Papworth has to be done fixture by fixture, on every floor where patients use water.
- precedent Other hospitals moving transplant and cystic fibrosis services into new buildings now have a documented case of a new water system linked to drug-resistant mycobacterial infections over six years.
The paper, published in Clinical Infectious Diseases [2], measures the effect of the controls in cases per year. "Following extensive control measures, including point-of-use filters and biocide treatment, incidence fell from 12.8 to 2.2 cases per year," the authors write [15]. That is a drop of about 83 percent [21]. A yearly count is not a rate per patient. It means lower risk for each patient only if the number of vulnerable patients passing through the building held roughly steady over the periods compared.
The failed attempt to treat the incoming supply [12] makes more sense next to the authors' account of where the strain turned up. "The outbreak strain had persisted and disseminated throughout the hospital, despite extensive control measures taken, with positive results obtained from four different floors," they report [11]. I'd take those two facts together as describing an organism settled in the building's own pipes and fixtures, beyond the reach of a dose added at the inlet. The measures that did cut cases all acted where patients met the water: filters on showers and basin taps, and bottled water during admission [10].
The UKHSA's later round of sampling, from 2022 to 2025, looked beyond the taps. Teams swabbed and sampled drains, showers and toilets, and took air samples above toilets after a flush [13]. The air sample tests a route of exposure that a tap filter does not touch. The results divided along that line [14].
The timing is where the evidence is weakest. Dr Ian Smith, Royal Papworth's medical director, said, "Infections can take a long time to present, sometimes many years" [17]. "People can acquire an infection and get symptoms straight away, some may not get symptoms until many years later, and some may never get any symptoms at all," he said [18]. The authors write that "No further case has been identified since June 2025, coinciding with a review of enhanced flushing" [16]. Coinciding describes a match in timing. Against a latency of years, a short run without new cases is weak evidence that exposure has ended. Smith says current and future patients are now safe, with ongoing vigilance, surveillance, and patient and staff education [1].
Whether new hospital buildings carry more of this risk than older ones would take a comparison across many sites. The investigation concerns one building [8], and it shows that a new hospital's water system can be the source of M. abscessus infections over six years [3].
The organism is a common contaminant that usually causes disease only through a wound or in a person with a weakened immune system, and it is multi-drug resistant [19]. Both women who died were treated for non-tuberculous mycobacterial pulmonary disease and died within a year of the bacterium first being detected [5]. The inquest heard of a third death but did not determine whether it was connected [6]. Solicitor Jatinder Paul said, according to the BBC, that patients had been admitted "in the hope of a better life" and that "The events that unfolded have been devastating for them and their families" [20].
What to watch
- Whether any new M. abscessus case linked to Royal Papworth appears after June 2025, given the multi-year latency Dr Smith described.
- Whether the full paper reports admissions data that let the 12.8 and 2.2 yearly figures be read as rates per patient.
- Whether other hospitals with new builds report sampling drains, toilets and post-flush air for non-tuberculous mycobacteria.