Chapter Twenty-Seven - Norovirus

Abstract

This chapter discusses Norovirus basic microbiology, natural history of the organism, clinical features and epidemiology of waterborne outbreaks, including transmission, distribution and persistence in the environment, removal by treatment and waterborne outbreaks. Clinical symptoms of norovirus are generally mild and self-limiting: nausea, vomiting, diarrhoea and fever that last for 1–3 days. Mortality is rare and has occurred mainly in people with pre-existing conditions and the elderly. Transmission is faecal–oral, either person-to-person or through a common source such as water or food. Aerosolization from vomitus is a source of infection as well. Secondary spread can be high in noroviruses. An infectious dose of 10 PCR-detectable units through oral ingestion has been shown. The lack of a robust cell culture technique has limited the amount of information on the presence of infective noroviruses in the environment. Using molecular methods, noroviruses have been identified in sewage, effluent, river and sea water.