ABSTRACT
A large outbreak of group A Streptococcus (GAS) pharyngitis occurred among 285 cadets at the Chulachomklao Royal Military Academy, Nakhon Nayok between September 22 and 27, 1996. An epidemiologic investigation was conducted to determine the source of infection. It seemed that respiratory droplets were the mechanism of spread, although foodborne transmission could not be excluded. To assess the presence of the outbreak strain in the community, conventional serotyping and molecular typing by emm sequencing were performed. The results demonstrated the advantage of molecular typing compared to serotyping and suggested that the outbreak was caused by the same strain. Interestingly, the involvement of the causative emm79 strain, which is an uncommon type of GAS disease, in a large number of patients may imply the invasive potential of this organism.