Characterization of rotavirus infection in a hospital neonatal unit in Pretoria,South Africa

Rotavirus infection in neonates is common and has been reported to be generally asymptomatic. In this longitudinal study, specimens were collected from 114 newborns in the Neonatal Unit at Pretoria Academic Hospital on a daily basis between January and May 1997. The babies remained in the ward between 1 week and 4 months. The stool specimens or rectal swabs were analysed for the presence of rotavirus antigen using a commercial enzyme-linked immunosorbent assay (Dako Rotavirus EIA) or electron microscopy. In total, 80 (70 per cent) of the neonates excreted rotavirus during their stay in the unit. There was a direct correlation between the length of stay in the ward and the shedding of rotavirus. The babies excreted rotavirus on average between 2 and 7 days. Rotavirus infection tended to occur within the first 2 weeks of life and was only observed once in most babies. Polyacrylamide gel electrophoresis of the RNA revealed the presence of two strains of rotavirus, with the differences in the RNA electropherotype occurring in the RNA segment triplet 7, 8 and 9. The VP7 serotype of the virus is encoded by one of these genes, and so the VP7 serotype of the virus was determined by monoclonal antibody and RT-PCR using VP7 serotype specific primers. The VP4 genotype of the viruses was also determined using RT-PCR of the VP4 gene to determine if a new rotavirus had been introduced to the ward. The strains were all characterized as G4P[6], which is similar to the antigenic make-up of the virus recovered 10 years before. This highlights the remarkable stability of rotavirus strains in neonatal units over long periods of time.