Report No FR0213
VIRUSES IN SURFACE WATERS -
OCCURRENCE AND ENVIRONMENTAL CONTROL
To report on the incidence and stability of enteric viruses in coastal waters, their effects on compliance with the EC bathing water Directive standards, and their implications for human health.
Under the Directive 76/160/EEC, enteroviruses must be absent from 95% of 10-litre samples, but monitoring is not required unless inspection shows that they are present or conditions have deteriorated. Development of monitoring capabilities and widespread virological sampling in the bathing season 1989 have shown that enteroviruses were detected at 73 out of 440 beaches in waters of satisfactory bacteriological quality. If the ubiquity and longevity of enteroviruses in the sea is confirmed it will have financial implications for proposed marine treatment schemes for bringing unsatisfactory beaches into compliance by 1995.
It is recommended that the following topics be considered for further research.
V RESUME OF CONTENTS
Current information on the incidence and sources of enteroviruses is reviewed. The numbers of viruses in sewage effluents were seen to depend on the virological quality of the raw sewage and on the type of treatment given. In general most types of treatment did not significantly decrease the virus content of wastewaters. Virus levels in rivers and coastal waters were found to be very variable and as a consequence unpredictable. The review highlights shortcomings in current analytical techniques, and a lack of standardisation of procedures could be seen to cause some of the apparent variation in virus levels.
Statistical analysis of the 1989 and 1990 bathing beach monitoring results demonstrated very clearly that there is no correlation between compliance with the faecal coliform and enterovirus standards. In practical terms this means that even if a beach complies with the faecal coliform standard the presence of viruses should still be suspected.
The available information on possible associations between microbiological quality of marine and fresh waters used for recreation and health effects reported by water sports participants was studied. It did not reveal a relationship in which viral conc entrations can be directly related to health effects. A surprising result from this detailed examination of data was a high degree of correlation between counts of faecal coliform bacteria and enterovirus concentrations when all available data were pooled. Such correlation was not seen in individual studies though.
Published data on viral decay rates was found to be too variable to allow a T90 value to be identified with confidence for use in predictive modelling studies. Future virological research needs are identified.
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