STUDY OF NORWALK VIRUS AND MEXICO VIRUS-INFECTIONS AT GA-RANKUWA-HOSPITAL, GA-RANKUWA, SOUTH-AFRICA

Small round-structured viruses (SRSVs) or Norwalk-like viruses have be en implicated as an important causative agent of gastroenteritis outbr eaks, We used the relatively newly developed recombinant enzyme immuno assays (EIAs) to determine the seroprevalence of Norwalk virus (NV) an d Mexico virus (MxV) in a family-based cohort and an antenatal clinic cohort at Ga-Rankuwa Hospital, Ga-Rankuwa, South Africa, High prevalen ces (96 to 99%) of anti-NV and anti-MxV antibodies were detected in bo th cohorts, We also investigated the pattern of antibody acquisition i n a cohort of infants and young children without gastroenteritis and f ound that by 48 months of age all children had acquired adult antibody levels to both these viruses, Lastly, we tested 276 stool specimens c ollected from infants and young children with gastroenteritis for the presence of NV or MxV antigen by recombinant EIAs to each virus, by el ectron microscopy (Ehl), and by reverse transcription (RT)-PCR, NV and MxV antigens were present in 1.8 and 4.3% of the stool specimens, res pectively, by the recombinant EIAs; 9.2% were positive for SRSVs by EM , and 25% of these SRSVs gave a positive result by RT-PCR for primer p air 35-36 directed to a region of the RNA-dependent RNA polymerase gen e. The seroprevalence studies indicate a high level of exposure to the se viruses in both children and adults, Although the viral antigens ar e not highly prevalent in diarrheal stools, it was determined by the t wo assays for NV and MxV that children are, nevertheless, infected ear ly in life.