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The survival of Noroviruses and potential viral indicators in sewage treatment processes and in the marine environment

Project Code: B05001

25/01/2011

Centre for Environment, Fisheries & Agriculture Science (CEFAS) Weymouth
Henshilwood, K

In the UK the main food safety risk associated with consumption of sewage polluted filter-feeding shellfish, such as oysters and mussels, is gastroenteritis caused by Norwalk-like virus (NLV). NLV is now known to be a very common infection in the community causing gastro-enteric illness in all age groups. As a consequence domestic sewage can be anticipated to be heavily loaded with NLVs. The protection of vulnerable shellfisheries is therefore dependant on adequate sewage treatment and inactivation of any residual pathogen load through effective dilution/dispersion of effluent in the sea following discharge. However, NLVs are non-culturable and molecular methods for their detection have only recently been developed. As a result, despite their acknowledged importance as etiological agents of viral illness, virtually nothing is known about their removal/inactivation during sewage treatment or in the environment following discharge. Available data mostly relates to conventional bacterial faecal pollution indictors such as E.coli or, to a lesser extent, culturable enteric viruses (e.g. polio virus). It is however not known whether such indicators adequately reflect the behaviour and survival of NLVs. Despite this uncertainty such information has, of necessity, been used to inform investment decisions on the most appropriate type and level of sewage treatment, the location of sewage discharges, and the priority given to control of intermittent discharges (such as combined storm overflows).

The main objective of this project was to provide information on the occurrence of NLVs in crude sewage effluents, their behaviour during passage through conventional sewage treatment processes (primary and secondary), their subsequent survival characteristics in the marine environment following discharge and their ultimate uptake by shellfish.

Final report

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