Report No DWI0791



Executive Summary

Under this contract the Public Health Laboratory Service (PHLS) was required to consider whether Escherichia coli 0157. astrovirus, calicivirus, microsporidia cyclospora and acanthamoeba might be considered as emerging pathogens according to the US Department of Heath and Human Services' definition. In addition adenovirus 40/41, Hepatitis A and E, other VTEC producing E.coli, aeromonas and yersinia were considered in varying degree. The study concluded that it is unlikely that a previously undescribed organism could gain access to, and survive within, a well controlled water distribution system and result in a previously unknown disease. E.coli 0157 VTEC had, on the evidence available, to be considered an emerging pathogen. which has on occasions been transmitted by water. The importance of VTEC other than E.coli has yet to be determined. Existing epidemiological and microbiological information leads to the conclusion that microsporidia and cyclospora are not currently significant as causes of infections in the UK population. It is most unlikely that the small number of infections reported arise from distributed water. Acanthamoeba must be considered as an emerging pathogen. However, its significance in the overall population is not great and infection could be controlled by better contact lens hygiene. Astroviruses. calicivirus and the viruses of Hepatitis A and E show no signs of becoming emergent pathogens.

The most appropriate way to address the potential problem of emerging pathogens is not by over zealous microbiological examination of water samples but by the diligent and detailed surveillance of cases of human infection and the investigation of all outbreaks which may be attributed to water. Because of the systems which the PHLS already has in place there is reason to believe that were a pathogen to emerge in the water distribution system it would be identified well before any problems became signif icant.

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