A relative risk was calculated (with 95% confidence interval) to assess significant differences in the incidence of acute gastroenteritis between HIV-infected and HIV-uninfected children. Estimated incidence rates for rotavirus infection in HIV-infected and HIV-uninfected children were calculated based on an assumed rotavirus prevalence of 14.8% in HIV-infected and

35.6% in HIV-uninfected. This was based on a study undertaken in the same population at CHBH which enrolled children aged 3 months to 4 years admitted with a diagnosis of gastroenteritis from October 1996 to December 1997. Investigations of these children had included obtaining blood specimens for HIV R428 testing and stool samples for microbiologic evaluation [4]. Characteristics of all children admitted with acute gastroenteritis were determined and then stratified by HIV infection status to investigate any differences between HIV-infected and HIV-uninfected children. Continuous variables

were compared using a t test for normally distributed data or Wilkoxon Ranksum test (Mann–Whitney) for data which was not normally distributed. The association between categorical variables was tested MLN0128 using the chi square test or Fisher’s exact test. All tests were 2-sided and a p-value <0.05 was considered statistically significant. The number of episodes of acute gastroenteritis was plotted by month to investigate seasonality of acute gastroenteritis during the study period, which was compared to that of total hospital admissions for the not same month and year. This was further stratified by HIV infection status to explore the association between

season and patterns of hospitalisation for acute gastroenteritis in HIV-infected and HIV-uninfected children. This secondary data-analysis was approved by the Human Research Ethics Committee (Medical) of the University of Witwatersrand. No further informed consent was required of the parents. There were a total of 9108 hospitalisations involving 6328 children under 5-years of age to CHBH over the study period, excluding repeat admissions occurring within two weeks of a previous hospitalisation. 1949 (21.4%) of the 9108 hospitalisations, involving 1761 participants, were for acute gastroenteritis. The majority (88.9%) of acute gastroenteritis episodes occurred in children less than two years of age, including 63.8% in children less than one year of age. Fig. 1 shows the number of hospitalisations for acute gastroenteritis as a proportion of total hospital admissions, stratified by age group. In those under 6 months of age 23.1% of total admissions were due to acute gastroenteritis, 33.0% in those aged between 6 and 12 months, 20.9% in those aged between 1 and 2 years and 10.2% in those aged between 2 and 5 years. Of the 1949 admissions for acute gastroenteritis, 504 (25.9%) occurred in HIV-infected children. HIV status was unknown or indeterminate in 244 (12.5%) of cases. Of the 1761 children admitted with acute gastroenteritis, 156 (8.