Long-term prevalence of group A type T-1 isolated from throats of healthy schoolchildren. Part II. Analysis by school classroom and sibling. Streptococcal Disease Study Group

Abstract

During the 7 years from September, 1980 to November, 1987, epidemiological study on hemolytic streptococci isolated from throat of schoolchildren in Osaka was carried out every two months. Group A streptococcus type T-1 strains were successively the most predominant type for the 3 years and 8 months since July, 1983.The beginning of these epidemia for type T-1 was the strain isolated from a girl in the third schoolclass on May, 1982. She became a long term carrier (two years) for type T-1 strain after this month. The infection was spread as follows; from her to her classmate, a boy, from him to his sister and from her to her classmate, a boy. Thus, the epidemia was spread throughout classmates, brothers and sisters. The long term carrier were distributed in every class in early 1983. Among those long term carriers, there were eight children who carried type T-1 strains during two years. As a result, the epidemic trend for type T-1 was further extended.Among the 62 pupils who were followed in every academic year since their entrance into the school, there were 34 or 36 cultures per child. Fourty-four of the 62 subjects had 5 or more group A positive cultures and nineteen had 3 or more type T-1.Twenty-four pair of brothers and sisters were compared with serotypes of group A. Coincidence of the serotypes among the pair was found in 21 pairs (87.5%). Seventeen of those 21 pairs were typed into type T-1.