Viruses in drinking-water. Reconsideration of evidence for postulated health hazard and proposals for virological standards of purity.

Stringent virological standards for drinking-water have been proposed by the World Health Organisation and by others, but there is no evidence of the spread of virus infection by drinking-water that has been adequately treated to conventional bacteriological standards. There is evidence for waterborne transmission of hepatitis and viral gastroenteritis but the case for the introduction of virological standards is critically examined. It is concluded that there is no evidence that drinking-water in the U.K. contributes to the spread of virus infection, and that the introduction of virological standards for drinking-water could not at present be justified. Moreover, in the absence of any information relating the degree of viral contamination to disease, there is no logical basis on which to set the level of a practical virological standard.