Epidemiology of a streptococcal outbreak in a school: attempt at control by mass prophylaxis with penicillin V

An attempt was made to abort an epidemic of streptococcal infection in a rural school including kindergarten through third grade by the use of mass, oral penicillin V prophylaxis for 10 days. Half of the classes received 200,000 units of penicillin V once daily and the others received two doses daily. In both instances, there was a decline in the carrier rates but neither regimen was entirely satisfactory. Unusual resistance to penicillin could not be demonstrated in streptococci isolated after the treatment period. Carrier studies were conducted in 124 families of children in the school sample. Prior to the prophylaxis regimen the carrier rate for Group A streptococci was 7% for adults more than 24 years of age and 24% in their children in the school being studied. Forty families which did not have children in the school also were cultured. None of the adults more than 24 years of age in this group was found to have streptococci in contrast with 4% of adults (cultured the same day) in the school-associated families. These observations tend to support the hypothesis that the school is the focus of infection and that families with children in school have a higher rate of infection than families without children in school. However, in both groups of families the adults appeared to be relatively resistant to infection. Within the school, the focus of infection appeared to be the individual classroom rather than the grade level. Rates of positive cultures for Group A streptococci in different classrooms within the same grade ranged from 0 to 71%. Numerous isolations of Group C streptococci were made in the school population. The age distribution paralleled the age distribution of the children from whom Group A organisms were isolated. In addition, titers of antistreptolysin-O in persons from whom Group C organisms were isolated were similar to those in persons with Group A strains. It is suggested that Group C infections may have contributed to the course of the epidemic.