Seroepidemiology of group A rotavirus in suburban São Paulo, Brazil.

Age-specific patterns of rotavirus infection were investigated using a randomly selected and representative sample of sera from a suburban community of São Paulo, Brazil screened for class-specific antibodies to group A rotavirus. Age-serology of anti-rotavirus IgG showed primary infection predominant in young infants with a median age of around 18 months consistent with IgM serology suggesting highest rates of recent infection between ages 4 and 48 months. Anti-rotavirus serum IgA prevalence increased gradually with age. Paired samples from infants, collected 1 month apart, indicated high exposure rates with seroconversion occurring in several infants during the reported low transmission season. Between 5 and 10% of adults had elevated IgM levels indicative of recent infection and, potentially, of an important contribution adults may play to rotavirus transmission. Further understanding of the dynamics of rotavirus transmission within populations, at group and serotype level, would benefit the design and monitoring of future immunization programmes.

Temporal and geographical distributions of human rotavirus serotypes, 1983 to 1988.

Between 1983 and 1988, subgroups and serotypes were determined for 907 of 1,084 clinical specimens of rotaviruses collected in various countries of Europe, North and South America, Africa, and Asia. Enhanced enzyme immunoassays based on monoclonal antibodies specific for rotavirus proteins VP6 and VP7 were used. Significant differences in the prevalent serotypes were detected from year to year in the United Kingdom and Brazil and also in different countries during the same year. Throughout the study, rotavirus serotype 1 was detected most often (53.8%), followed in frequency by serotype 2 (17.8%), serotype 3 (12.1%), serotype 4 (11.1%), and serotypes other than 1 to 4 (5.1%). No individual serotype was found to predominate consistently in any one location. In the United Kingdom, rotavirus serotypes varied in prevalence in a regular but not predictable way. We suggest that a similar epidemiology might be found in other settings. Seventeen unusual strains were detected. Of these, five strains did not react with reference monoclonal antibodies specific for subgroup I and subgroup II, but they reacted with rotavirus group A-specific polyclonal and monoclonal antibodies; four strains were of subgroup II, serotype 2, and at least one had a "long" electropherotype; two strains were of subgroup I, serotype 2 with a long electropherotype; and one strain was of subgroup I, serotype 3. Five group C rotaviruses were detected.

Epidemiology of rotavirus subgroups and serotypes in Belem, Brazil: a three-year study.

Rotavirus subgroups and serotypes were determined in 61 rotavirus-positive faecal samples obtained from children living in Belém, Brazil, followed up from birth to 3 years of age. Fifty-five (90%) of the specimens were subgrouped and the serotypes of 30 (49%) of them were determined. Subgroup II was detected in 49 (89%) of the 55 subgrouped strains. Serotype 1 was present in 15 (50%) of the 30 serotyped samples; serotypes 2, 3 and 4 were found in 30%, 3.3% and 16.7% respectively, of these specimens. Absence of Vp7, the major outer capsid glycoprotein, did not allow serotyping in 21 (34.4%) of the 61 rotavirus-positive specimens, and an unidentifiable new serotype was found in faeces of one child. In addition, 4 samples were classified as subgroup II serotype 2 (which is very unusual). Twelve (80%) of the 15 serotype 1 (subgroup II) specimens were collected from children (5 of them asymptomatic) during their first year of life. All 9 serotype 2 (subgroups I, II, or not determined) samples were detected during the second and third years of life, 7 (77.8%) of them were related to apparent infections. The 5 serotype 4 (subgroup II) samples were obtained throughout the study period, and were associated with both symptomatic (3 cases) and asymptomatic infections. Thirteen children had more than 1 rotavirus infection. Three had 3 successive infections. In 3 cases, the initial infection (either symptomatic or asymptomatic) caused by serotype 1, was followed by a subsequent diarrhoeic episode associated with serotype 2.

Clinical efficacy of the RIT 4237 live attenuated bovine rotavirus vaccine in infants vaccinated before a rotavirus epidemic.

In a randomized, double-blind, placebo-controlled trial, 331 infants aged 6 to 12 months received orally, at an interval of 1 month, either two doses of live attenuated bovine rotavirus vaccine strain RIT 4237 or equivalent placebo. The vaccinations were carried out during September to November, a non-rotavirus season; only three cases of rotavirus diarrhea occurred in the study group before the vaccinations were completed. During the epidemic season from December to May, 31 patients with clinically significant rotavirus diarrhea required therapy. Five of these were among the 168 vaccine recipients, and 26 among the 160 placebo recipients (P less than 0.001), giving a vaccine protection rate of 82%. The incidence of clinically significant diarrhea from all causes was reduced by 76% in the vaccinees. As determined by an enzyme immunoassay antibody test with homologous virus antigen, seroconversion after vaccination was obtained in 53% of the initially seronegative infants. Clinical protection correlated well with seroconversion, but the vaccinees who failed to seroconvert also had less rotavirus diarrhea than the placebo recipients, suggesting that immunity may be mediated by factors other than serum EIA antibody. Seventeen of the 23 rotavirus isolates in the epidemic season that were typed were of serotype 1, two were of serotype 2, and four were of serotype 3. The protection rates against clinically significant diarrhea were 72%, 100%, and 100% for serotypes 1, 2, and 3, respectively. We conclude that epidemic infantile winter diarrhea associated with human rotaviruses can be significantly reduced by vaccination with the live attenuated RIT 4237 bovine rotavirus vaccine before the epidemic season.

An outbreak of rotavirus diarrhea among a nonimmune, isolated South American Indian community.

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.