A community outbreak of invasive and non-invasive group A beta-haemolytic streptococcal disease in a town in South Wales

An increase in the incidence of invasive and non-invasive infections caused by group A beta-haemolytic streptococci (GAS) was noted in and around the town of Glynneath (population approx. 4000) in West Glamorgan, South Wales between 1 January and 30 June 1995. A total of 133 cases was ascertained wi th 127 (96 %) occurring between 1 March and 30 June 1995. Six patients had invasive disease (one died) and all presented at the peak of the outbreak. There were 127 non-invasive cases of whom 7 were hospitalized. The outbreak was investigated to determine its extent and whether it was caused by a si ngle M-serotype of GAS. Serotyping showed that 13 different M-serotypes wer e involved with the M1 serotype predominating. The overall incidence of GAS invasive disease in West Glamorgan (population 365 000) increased sevenfol d from a crude incidence of 0.5/10(5) per year in 1994 to 3.5/10(5) per yea r in 1995, but fell back to 0.75/10(5) per year in 1996. Eighty-two (80 %) out of 102 individuals affected by GAS replied to a health questionnaire; s ore throat was the commonest symptom reported (97 %). Thirty-nine of these index cases identified at least one other member of their household who had experienced similar symptoms. The interval between the onset of illness in members of a single household was 0-83 days with a mean of 22 days. The me an duration of illness was 13.5 days and 61% of patients were treated with penicillin V for a mean duration of 9.3 days. Twenty-one per cent of GAS is olates were erythromycin-resistant and the M4 and M6 serotypes were especia lly resistant to erythromycin (87.5 and 100% resistance, respectively). Pen icillin V failed to eradicate GAS from the throats of 25 % of assessable pa tients. In this community, an outbreak of non-invasive disease caused by GA S was linked in time and place with an outbreak of serious invasive disease .