A lack of significant association between the electropherotype or G-serotype of the infecting strain and disease severity of rotavirus gastroenteritis.

Despite many previous studies, the question has not been settled as to whether some human rotavirus strains are more virulent than others. Since disease severity is most clearly reflected by the hospitalization status of the infected children, we examined whether there was any difference in the distribution of dominant strains between inpatient and outpatient groups. The study population comprised 763 children with acute diarrhea who were treated at a general hospital in Honjo City, Akita, Japan, during 1986-1997. Rotaviruses from stool specimens were classified into 77 electropherotypes using polyacrylamide gel electrophoresis. A single dominant strain or two co-dominant strains circulated simultaneously with some infrequent strains in most rotavirus seasons. Over the 11 rotavirus seasons, there was no significant difference in the relative frequencies of 15 rotavirus strains between the inpatient and the outpatient groups when strains of rotavirus were defined by their electropherotypes in polyacrylamide gel electrophoresis. However, infection with one G1 strain that co-dominated with a G4 strain carrying an identical electropherotype except the VP7 gene resulted in a statistically significantly reduced risk of hospitalization. There was no significant difference in the relative frequencies of four major G-serotypes or long/short RNA pattern. We conclude that the virulence or disease-causing potential of human rotavirus is not substantially different in the majority of strains.