Background: During September 2021 increasing numbers of emm 77.0 GAS isolates were observed from people living in SW England. An Incident Management Team was established to undertake a risk assessment, guide investigations and implement control measures.
Materials/methods: All GAS isolates referred from SW England to the UK Health Security Agency streptococcal reference laboratory were characterised by emm gene sequence typing. Whole genome sequencing (WGS) was used to ascertain relatedness of isolates. Risk factor information were extracted from the Health Protection Team case management system. Epidemiological data were analysed descriptively.
Results: Between 01-12-2020 and 31-12-2021, there were 119 isolates of GAS (70 invasive, 44 non-invasive, 5 unknown) sent to the reference laboratory from SW England. twenty-eight individuals had infections with emm 77.0. Of these, 14 (50%) isolates were recovered from people who injected drugs (PWID) Individuals infected with emm 77.0 were predominately male (74%) and had a median age of 42 years (range 4-85 years). WGS of 30 strains revealed numerous related clades within 0-3 SNPs. The majority (n=26) were MLST904 and core genome SNP variation suggested a recent geographically linked clonal expansion concentrated in four urban areas, indicative of a strain which has become established within the population.
Conclusions: These findings indicate clonal expansion of emm 77.0 causing an increasing burden of severe, invasive GAS infections in South West England. Reinforcing infection control measures in vulnerable populations remains challenging and requires a multidisciplinary approach with a strong focus on provision of wound care and continued surveillance.