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Guidelines for drinking-water quality: Fourth edition incorporating the first and second addenda [Internet]. Geneva: World Health Organization; 2022.

Cover of Guidelines for drinking-water quality

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

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Table 7.1Pathogens transmitted through drinking-watera

PathogenType species/genus/groupbHealth significancecPersistence in water suppliesdResistance to chlorineeRelative infectivityfImportant animal source
Bacteria
Burkholderia B. pseudomallei HighMay multiplyLowLowNo
Campylobacter

C. coli

C. jejuni

HighModerateLowModerateYes
Escherichia coli – DiarrhoeagenicgHighModerateLowLowYes
E. coli – EnterohaemorrhagicE. coli O157HighModerateLowHighYes
Francisella F. tularensis HighLongModerateHighYes
Legionella L. pneumophila HighMay multiplyLowModerateNo
Mycobacteria (non-tuberculous)Mycobacterium avium complexLowMay multiplyHighLowNo
Salmonella typhiHighModerateLowLowNo
Other salmonellae

S. enterica

S. bongori

HighMay multiplyLowLowYes
Shigella S. dysenteriae HighShortLowHighNo
Vibrio V. cholerae O1 and O139HighShort to longhLowLowNo
Viruses
AdenoviridaeAdenovirusesModerateLongModerateHighNo
AstroviridaeAstrovirusesModerateLongModerateHighNo
CaliciviridaeNoroviruses, SapovirusesHighLongModerateHighPotentially
HepeviridaeHepatitis E virusHighLongModerateHighPotentially
PicornaviridaeEnteroviruses, Parechoviruses, Hepatitis A virusHighLongModerateHighNo
ReoviridaeRotavirusesHighLongModerateHighNo
Protozoa
Acanthamoeba A. culbertsoni HighMay multiplyHighHighNo
Cryptosporidium C. hominis/parvum HighLongHighHighYes
Cyclospora C. cayetanensis HighLongHighHighNo
Entamoeba E. histolytica HighModerateHighHighNo
Giardia G. intestinalis HighModerateHighHighYes
Naegleria N. fowleri HighMay multiplyLowModerateNo
Helminths
Dracunculus D. medinensis High Moderate Moderate High No
a

This table contains pathogens for which there is some evidence of health significance related to their occurrence in drinking-water supplies. More information on these and other pathogens is presented in chapter 11.

b

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

c

Health significance relates to the incidence and severity of disease, including association with outbreaks.

d

Detection period for infective stage in water at 20 °C: short, up to 1 week; moderate, 1 week to 1 month; long, over 1 month.

e

Within pathogen species and groups, there are likely to be variations in resistance, which could be further impacted by characteristics of the water supply and operating conditions. 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 Legionella and mycobacteria, will be protected from chlorination.

f

From experiments with human volunteers, from epidemiological evidence and from experimental animal studies. High means infective doses can be 1–102 organisms or particles, moderate 102–104 and low > 104.

g

Includes enteropathogenic, enterotoxigenic, enteroinvasive, diffusely adherent and enteroaggregative.

h

Vibrio cholerae may persist for long periods in association with copepods and other aquatic organisms.

From: 7, Microbial aspects

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