The role of household contacts in the transmission of group A streptococci.

The intrafamilial spread and recurrence of group A beta-haemolytic streptococci (GAS) infections was investigated. The evaluation was based on 114 patients and their families treated with penicillin for 5 days and followed for 1 month. GAS of the same T-type as that of the isolate from the index case were found in other family members in 33% of the families. Genetic finger-printing using RFLP was performed on 33 of the isolates. The mothers dominated among the index cases, 40 patients experienced recurrences, 27 of them were clinical 28 recurrences occurred within 10 days after the end of treatment. Of 20 T-typed patients with early clinical treatment failures, infected family members were detected in 16 families (p < 0.001). In 19% of the patients GAS could be isolated from the nose. These patients had more ill family members than did other patients. An extensive intrafamilial streptococcal spread was found. Most recurrences of GAS pharyngotonsillitis after penicillin treatment are probably due to "ping pong" infection from family members.