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Group A rotaviruses are the most important agents of severe diarrhea in children and infants worldwide. The aim of present study was to identify rotavirus G serotypes and P[],G genotypes in cases of reinfection among children who participated in a vaccine trial with the tetravalent rhesus-human reassortant rotavirus vaccine (RRV-TV 4 x 10(4) pfu/dose) in Belém, Brazil. From July 1990 to June 1992, 540 children received, at their first, third and fifth months of life, oral doses of either vaccine or placebo. A total of 90 rotavirus diarrheal episodes among children who completed the three-dose vaccination schedule were recorded. We studied 11 reinfection rotavirus cases among five children (three female and two male). Fecal specimens were tested by using a enzyme immunoassay (IDEIA Rotavirus), followed by EIA with monoclonal antibodies to determine infecting serotypes Gl, G2, G3 and G4 and subgroups I and II. The viral dsRNA was extracted and electrophoresed through polyacrylamide gel and then subjected to reverse-transcription-polymerase chain reaction and nested-PCR for the determination of Gl, G2, G3, G4, G5 and G9 and P[4], P[6], P[8] and P[9] rotavirus genotypes. A total of 11 cases of reinfection (12 per cent) occurred among five children, three from the placebo group and two from the vaccine group. In four of the cases of reinfection G serotypes and P[],G genotypes were as follows: for the first and second infections, respectively: (1) G2/P[4],G2 and Gl/P[4],G1; (2) G2/P[4],G2 and G2/P[6],G5; (3) G2/P[4],G2 and G1/P[8],G1; and (4) G2/P[8],G1 and G1/P[8],G1. A fifth child had three successive infections caused by serotypes/genotypes G1/P[8],G1, in the first and second infections, and G2/P[4],G2 in the third infection. The common genotypes and unusual genotypes were detected in 8 (73 per cent) and 3 (27 per cent) of the isolates, respectively. With regards to the clinical severity, in two children a score indicated moderate/severe disease in both first and second infections. One child had three successive infections; the first episode was moderate/severe, the second very severe and the third was not available. In contrast, in two other children, the first episode was very severe, and the second episode was moderate/severe in one child and data was not available for the other child. The results obtained in the present investigation underscore the need to broaden our knowledge of the immunity in rotavirus reinfection. This should be useful regarding future rotavirus vaccination strategies in Brazil.

During July-August 1977, an outbreak of acute diarrhea occurred in an unusually isolated population, the Tiriyó Indians, who live in the north of Pará, Brazil, near the border with Surinam. Diarrhea was reported by 157 (70%) of the 224 Indians living in the village during the epidemic. There was one fatal case in a one year old child. Rotavirus was detected by electron microscopy in one fecal specimen collected from an acute case of diarrhea. Seroconversions were noted in 127 out of 168 (75.6%) paired serum samples tested for rotavirus antibody by counter-immunoelectrophoresis. With immunofluorescence based neutralization tests, rotavirus serotype 1 (Birmingham) was shown to be associated with the outbreak. The infection also boosted type 3 antibodies but this was most apparent in persons with pre-existing type 3 titers and the boost was not as great as with type 1. All age groups were affected. The proportion symptomatic was greatest in young children.

From December 1982 to March 1986 a group of 80 children between 0 and 3 years old who lived in the peripheral area of Belém, Brazil, were followed up for episodes of diarrhoea. A total of 441 diarrhoeal episodes were recorded and 36 (8.2%) were associated with rotavirus. This agent was the only pathogen in 50% of rotavirus-related episodes of acute diarrhoea, and strains were characterized by analysis of RNA in polyacrylamide gels. Forty-one belonged to subgroup II (long pattern) and five to subgroup I. Reinfections by rotavirus were noted in 12 children involving either the same or different subgroups. Ten distinct electrophoretypes were detected in the study period and the predominant one had the '1N2L' profile. The cumulative age-specific attack rate for diarrhoea reached 2.8 by the end of the first year of life; a frequency of 2.3 episodes of diarrhoea per child per year was observed throughout the complete investigation. In comparing the age-specific attack rates for diarrhoea between breast-fed and bottle-fed children, a peak at 6 months of age was noted in the former, and at 1 month in the latter. A comparison by Fischer's exact test (P = 0.21) provided no evidence for protection against clinical rotavirus disease by maternal milk. By the same test, however (P = 0.021), we found significant evidence that early rotavirus infections were more likely to be asymptomatic and that infections after 4 months were more likely to be symptomatic. The clinical picture in children with rotavirus-related diarrhoea was more severe than in those suffering from acute diarrhoea due to another agent.

Atypical rotaviruses were detected in faeces from two diarrhoeic children living in Belém, Pará, Brazil. Rotavirus particles were detected by electron microscopy and the RNA electrophoresis showed patterns which were compatible with group C rotaviruses. Tests for the presence of group A antigen by enzyme-linked-immunosorbent assay (ELISA) were negative. The two children had three successive rotavirus infections and in both cases the atypical strains were excreted at the time of the third infection, causing a mild and short-lasting disease.