Norwalk and "Norwalk-like viruses" in epidemic gastroenteritis.

Despite the lack of a cell culture or animal model system, the past decade has seen tremendous advances in our understanding of NLV. Prior to 1990, the only nucleotide sequence information for caliciviruses was from viruses isolated from animals. There are now sequences available for more than 100 NLV isolates and more are rapidly accumulating. Such information is being used for development of new and more sensitive diagnostic assays. The CDC, under the National Food Safety Initiative and in cooperation with state and local governments, is working toward implementing routine surveillance and outbreak responses to limit or prevent widespread illness from the same identified source. Such increased surveillance and continued epidemiologic studies are necessary and critical to assess the risks and contain food-borne and water-borne outbreaks caused by the NLVs.