Astroviruses.

Human astroviruses are members of the Astroviridae family. They are non-enveloped viruses possessing a single-stranded RNA of positive polarity as their genome. The development of sensitive tests for the presence of astrovirus-for example, using group reactive monoclonal antibodies-has led to the conclusion that astroviruses are the cause of more cases of childhood diarrhea. Astroviruses have also been identified as the cause of major outbreaks of diarrhea and vomiting. Different serotypes of human astrovirus have been defined based on immune electron microscopy, neutralization tests, and type-specific enzyme immune assays (EIAs). Eight different serotypes have been identified and it has been shown that differences in the sequences of reverse transcription-polymerase chain reactions (RT-PCR) products from a region within open reading frame 2 (ORF2) correlated precisely with antigenic types determined by type-specific EIA.