Abstract
The relation of carriers to the occurrence of outbreaks of streptococcal pharyngitis among groups of rheumatic children during a 6-year period is reported. Major and minor outbreaks as well as sporadic cases were observed. Major outbreaks were due to a Group A streptococcus of a single type not previously present and were not preceded by a rise in carrier rate. Minor outbreaks were preceded by a slow spread from carriers to other individuals without at first causing infection. Subsequently, a small number of clinical cases due to these types developed. Sporadic cases arose directly from carriers and were not preceded by a dissemination of the streptococci to healthy individuals. The length of the carrier state was also studied.