FIG. 1. Distribution of genotypes of NLV (top) and SLV (bottom) in cases of gastroenteritis detected during a physician-based study in The Netherlands from 1996—1998. For genotype designations see Table 1.
in the community study, as was noted earlier from Sweden and the UK, suggesting that these strains are less virulent (Vinje et al 2000a). In the near future we will analyse the epidemiological database in combination with genotyping information for such genotype-specific characteristics.
The sudden emergence and spread of a single strain raises important questions about the mode of transmission that allowed these events to occur, especially since no obvious epidemiological links were found between most outbreaks. Besides the possibility of large scale food- or waterborne transmission, the possible existence of an animal reservoir, or the existence of variants with altered tissue tropism (e.g. favoring spread by the respiratory route) are working hypotheses that need to be addressed in future studies. Recently, a European consortium with participants from nine countries has initiated a project aimed at developing standardized surveillance for enteric viruses in Europe, including a database that will be used as an early warning tool. Our goal is to thus provide a framework for studies addressing the above hypotheses.
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