Norwalk virus in Norway: an outbreak of gastroenteritis studied by electron microscopy and radioimmunoassay.

An outbreak of acute gastroenteritis affected approximately half of 40 children staying at a holiday centre in Southern Norway. By direct electron microscopy Norwalk-like viruses were demonstrated in 4/8 available stool specimens. No other pathogens were detected. Antibody against these viruses was demonstrated by immune electron microscopy in all of 7 convalescent phase sera but in none of 11 acute phase sera collected. Radioimmunoassay examination showed a rise in titre of Norwalk virus antibody in 6 available paired sera. This outbreak of Norwalk virus gastroenteritis in Norway was thus documented by a combined use of direct and immune electron microscopy and radioimmunoassay.