Table 7.2Microorganisms for which transmission through drinking-water has been proposed but for which evidence is inconclusive or lackinga

MicroorganismType species/genus/groupbWaterborne transmission evidence (or epidemiological features)Presence and behaviour in water suppliesResistance to chlorinec
Bacteria
Acinetobacter A. calcoaceticus baumannii complex Possible issue in health-care facilities (non-gastrointestinal)Common and can multiplyLow
Aeromonas A. hydrophila Clinical isolates do not match environmental isolatesCommon and can multiplyLow
Enterobacter E. sakazakii Infection associated with infant formula; no evidence of waterborne transmissionUnlikelyLow
Helicobacter H. pylori Suggested, but no direct evidence; familial transmission primary routeDetected, survives for limited timeLow
Klebsiella K. pneumoniae Possible issue in health-care facilities (non-gastrointestinal)Can multiplyLow
Leptospira L. interrogans No evidence of transmission through drinking-water ingestion. Primarily spread by contact with contaminated surface water; outbreaks associated with floodingCan survive for months in waterLow
Pseudomonas P. aeruginosa Possible issue in health-care facilities (non-gastrointestinal)Common and can multiplyModerate
Staphylococcus S. aureus No evidence of transmission through drinking-water; hands are the most important sourceCommon and can multiplyModerate
Tsukamurella T. paurometabola Possible issue in health-care facilities (non-gastrointestinal)Common and can multiplyUnknown
Yersinia Y. enterocolitica Species detected in water probably nonpathogenic; food is the primary sourceCommon and can multiplyLow
Viruses
FiloviridaeEbola virusNo evidence of transmission through drinking-waterUnlikelyLow
OrthomyxoviridaeInfluenza virusesNo evidence for waterborne transmissionUnlikelyLow
CoronaviridaeSevere acute respiratory syndrome (SARS) coronavirusesSome evidence for transmission via inhalation of dropletsUnlikelyUnknown
Picornaviridae/KobuvirusAichivirusPresent in fecal wastes, wastewater and sometimes contaminated drinking waterLikely present in faecally contamined waterModerate
Protozoa
Balantidium B. coli One outbreak reported in 1971DetectedHigh
Blastocystis B. hominis Plausible, but limited evidenceUnknown, persistenced likelyHigh
Isospora I. belli Plausible, but no evidenceUnknownHigh
Microsporidia–Plausible, but limited evidence; infections predominantly in persons with acquired immunodeficiency syndrome (AIDS)Detected, persistence likelyModerate
Toxoplasma T. gondii One outbreak reported in 1995LongHigh
Helminths
Fasciola

F. hepatica

F. gigantica

Plausible, detected in water in hyperendemic regionsDetectedHigh
Free-living nematodes (other than Dracunculus medinensis)–Plausible, but transmission primarily associated with food or soilDetected and can multiplyHigh
Schistosoma

S. mansoni

S. japonicum

S. mekongi

S. intercalatum

S. haematobium

No evidence of transmission through drinking-water ingestion. Primarily spread by contact with contaminated surface water in communities with inadequate access to safe drinking-waterLife cycle involves animal and snail hosts; can be released into water following reproduction in freshwater snailsModerate
a

More information on these and other pathogens is presented in chapter 11.

b

The type species listed (e.g. H. pylori) are those most commonly linked to waterborne transmission but other species may also cause disease.

c

Resistance is based on 99% inactivation at 20 °C where, generally, low represents a Ct99 of < 1 min.mg/L, moderate 1–30 min.mg/L and high > 30 min.mg/L (where C = the concentration of free chlorine in mg/L and t = contact time in minutes) under the following conditions: the infective stage is freely suspended in water treated at conventional doses and contact times, and the pH is between 7 and 8. It should be noted that organisms that survive and grow in biofilms, such as Pseudomonas aeruginosa, will be protected from chlorination.

d

Persistence means survival for 1 month or more.

From: 7, Microbial aspects

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Guidelines for drinking-water quality: Fourth edition incorporating the first and second addenda [Internet].
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