Increasing incidence of invasive group A streptococcal (iGAS) outbreaks in England 2015-2019.

Early detection and active management of invasive group A Streptococcus (iGAS) infection outbreaks are essential. Here, we describe the changing epidemiology of outbreaks of iGAS in England between 2015 and 2019, a period of increasing incidence of iGAS infection. Data on iGAS infections were extracted from national public health management records and laboratory records. Outbreaks were described in size, duration, setting, and emm type. Overall, 194 outbreaks were identified, and reports increased each year, from 16 outbreaks in 2015 to 61 in 2019. The median outbreak size was 3 cases (n = 37; 19%), with 27% of outbreaks recording 4-10 cases (n = 53) and 7% recording more than 10 cases (n = 13). Outbreak duration ranged from 0 to 170 weeks (median 7). Settings of outbreaks changed over the study period, with increasing numbers observed in multiple settings. This study provides new insights into the changing burden of iGAS infection and outbreaks in England.