An increase in the incidence of invasive and non-invasive infections
caused by group A
β-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 with 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 single M-serotype
of GAS. Serotyping
showed that 13 different M-serotypes were involved with the M1 serotype
predominating. The
overall incidence of GAS invasive disease in West Glamorgan (population
365000) increased
sevenfold from a crude incidence of 0·5/105 per year
in 1994
to 3·5/105 per year in 1995, but
fell back to 0·75/105 per year in 1996. Eighty-two
(80%)
out of 102 individuals affected by
GAS replied to a health questionnaire; sore 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
mean 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 isolates were erythromycin-resistant and the
M4 and M6
serotypes were especially resistant to erythromycin (87·5 and 100%
resistance, respectively).
Penicillin V failed to eradicate GAS from the throats of 25% of assessable
patients. In this
community, an outbreak of non-invasive disease caused by GAS was linked
in time and place
with an outbreak of serious invasive disease.