Waterborne Enteric Viruses: Diversity, Distribution, and Detection

Enteric viruses are a leading cause of gastroenteritis and they constitute a diverse group. The viruses commonly implicated in gastroenteritis (cases or outbreaks) are classified into the families Picornaviridae (polioviruses, enteroviruses, coxsakieviruses, and echoviruses), Adenoviridae (adenovirus 40 and 41), Caliciviridae (noroviruses, Sapporoviruses,), and Reoviridae (reoviruses). Although enteric virus infections are mainly associated with diarrhea and self-limiting gastroenteritis in healthy humans, they have also been linked to aseptic meningitis, encephalitis, myocarditis and insulin-dependent diabetes. Currently, about 140 waterborne viruses are known to infect humans. The waterborne viruses not only show wide diversity in the illness (including diarrhea, fever, hepatitis, paralysis, meningitis, respiratory and heart diseases, they also show broad diversity in their size, shape, infection process and replication mechanisms. Most of waterborne enteric viruses have icosahedral capsid; however, the structural feature on the surface of capsids varies among different virus groups. The rotavirus capsid is composed of three concentric protein layers and the outermost layer comprises the proteins VP4 and VP7. The PV4 forms spike like structures which are responsible for virus attachment to host cell. Adenovirus has an icosahedral capsid composed of hexon the major capsid protein. In addition, capsid has penton with elongated fibers projecting out of each penton. The distal ends of these fibers have a globular “knob” which functions as the major attachment site for host cell receptors. In general, the members of enteroviruses and caliciviruses /norovirus have capsid with less pronounced surface features; but members of these groups have significantly different annotation of their capsid.