[Seroepidemiology of human rotaviruses in a community of the Avellaneda district, Province of Buenos Aires].

The results obtained during a prospective study performed in 49 families of the Avellaneda District, Buenos Aires Province, in order to known the seroepidemiology of human rotaviruses under natural conditions were described. Families which included a pregnant woman, were voluntarily recruited. The newborn was studied together with its family until two years of age, in order to assess the moment of the primary rotavirus infection. Feces from every person with gastrointestinal symptoms were obtained for rotavirus diagnosis. Blood samples from every member of the family were obtained since their recruitment and each 6 months until the newborn reached two years of age. Rotavirus infections were established by determining the amount of circulating rotavirus IgG antibodies in paired serum samples using ELISA. In all, 502.2 six-month periods with paired serum samples were studied. Most of the infections detected during the first year of life were primary infections (0.64 cases per child-year; 91.3% in seronegative children; p less than 0.005). The peaks of rotavirus diarrhea incidence were observed at the same age (0.25 cases per child-year; p less than 0.01). It must be stated that 51.9% of the newborns presented circulating anti-rotavirus IgG antibodies transmitted by the mother; 72% were breastfed for a mean period of 9.7 months. The total incidence of rotavirus infections was 0.63 cases per person-year, without significant variations for each age group. Most of them were asymptomatic cases and 61.6% were reinfections. These results show the high endemicity of human rotavirus in our population where siblings and adults act as reservoirs of the infection. Finally we found a significant relation between the level of circulating anti-rotavirus antibodies and the resistance to infection and illness caused by rotavirus during the six-month periods studied with paired serum samples (p less than 0.005 for infection; p less than 0.03 for diarrhea). The incidence of rotavirus infection did not seem to be statistically different among all the age groups. As we found a high incidence of reinfections and we were able to determine the total decrease in the level of serum anti-rotavirus IgG antibodies in 5% of the infections one year after the seroconversion was detected, we postulate a short duration of high antibody levels and protection associated with circulating anti-rotavirus antibodies.