World Health Organization 2025. https://doi.org/10.2471/B09259.
Highlights:
- There is moderate evidence for transmission of non-tuberculous Mycobacterium (NTM)
from drinking-water systems in buildings and devices supplied with drinking-water. Most
cases associated with water are sporadic, but a number of outbreaks have been reported in
healthcare facilities, associated with a single facility or a specific procedure.
- The atypical or non-tuberculous species of Mycobacterium are natural inhabitants of a
variety of water and soil environments. This contrasts with the “typical” species of
Mycobacterium that have only human or animal reservoirs (e.g. Tuberculosis or Leprosy).
- Principal routes of waterborne infection are inhalation of aerosols and contact with or
ingestion of water colonized by NTM.
- NTM diseases are commonly asymptomatic but can cause infections of the respiratory, gastrointestinal, and genitourinary tracts, as well as a broad range of diseases involving the skeleton, lymph nodes, skin and soft tissues.
- The incidence of NTM-mediated disease is increasing in high-income countries. The
incidence in the rest of the world is unknown due to limited systematic reporting and surveillance.
- The infective dose is not known and due to the influence of host factors is likely to vary
depending on the susceptibility of those exposed. In addition, the virulence of individual
species and strains is likely to vary.
- There are culture-based methods for detection of NTM although isolation can be
challenging due to the slow growth of some species in culture media. Molecular methods are available for detection and speciation.
- NTM thrive in engineered water environments, (e.g. drinking water treatment and distribution systems and building water systems), which provide suitable conditions to support the survival and growth of NTM in biofilms.
- Within a water safety plan, control measures for NTM should focus on a combination of
measures to limit their survival during treatment and their growth in biofilms, including in
free-living amoebae and other protozoa.
- NTM are highly resistant to oxidizing disinfectants such as chlorine but are sensitive to UV light.
- As NTMs are non-faecal, environmental organisms that can survive and grow in water and
are resistant to disinfection, E. coli (or alternatively, thermotolerant coliforms) is not a
suitable indicator for the possible presence or absence of NTM in drinking-water.
