Outbreak of Streptococcus pyogenes infections in a geriatric hospital and control by mass treatment.

Two outbreaks of Streptococcus pyogenes infection occurred in a geriatric hospital, the first involving one ward only, the second a few weeks later, affecting two. Altogether 17 patients and 6 members of staff were carriers or were infected. All strains were indistinguishable.Extensive investigation of the environment and screening of 120 staff and patients did not reveal a common source. The usual methods of isolation and treatment of cases or carriers and swabbing of contacts failed to stop the outbreak, but 'mass treatment' of all 32 patients in those wards was successful.