Background
An array of control measures to slow the spread of SARS-CoV-2 were implemented in the UK from March 2020, providing a unique opportunity to assess their impact on transmission of other pathogens.
Methods
The following national surveillance data were analysed: i) statutory scarlet fever notifications, ii) laboratory reports of invasive group A streptococcal (iGAS) infection, and iii) outbreaks of iGAS infection recorded by local health protection teams.
Results
Following the first lockdown on 23 March 2020 (week 13), including school closure, scarlet fever activity rapidly declined, from a mean of 648 cases/week in the preceding 4 weeks to 96 cases in week 14. Notifications remained exceptionally low: 1,623 cases reported for weeks 14 to 13 in 2020/21 vs 17,528 in 2019/20. iGAS infections declined more gradually, from 73 cases in week 11 to 23 cases by week 17, with 10-30 cases/week for the remainder of 2020 and 2021. Outbreaks of iGAS infection continued to be documented throughout the pandemic although declining from 69 per annum in 2018-2019 to 38 and 48 in 2020 and 2021. Outbreaks occurred across all settings although there was a notable reduction in hospital/maternity outbreaks.
Conclusions
Closure of schools and wider measures limiting social mixing resulted in rapid reduction of GAS transmission. Continued low levels of scarlet fever after school reopening suggests cohorting and use of face masks were effective in supressing transmission in schools. Whilst stepped up infection prevention and control measures may have reduced transmission of GAS infection in hospitals, less impact was evident in care homes.