Impact of the COVID-19 Pandemic on Group A Streptococcal Necrotizing Soft Tissue Infections: A Retrospective Cohort Study

Background. Necrotizing soft tissue infections (NSTIs) are often caused by group A Streptococcus (GAS). As the number of invasive GAS infections decreased during the coronavirus disease 2019 (COVID-19) pandemic restrictions, this study aimed to compare the occurrence of GAS-NSTIs before, during, and after the COVID-19 pandemic restrictions. Methods. This retrospective cohort study included adult patients with NSTIs admitted to the intensive care unit (ICU) of the University Hospital Zurich, Switzerland, from July 2008 to December 2023. NSTI cases were categorized as pre-, during, and postrestrictions. The primary outcome was the proportion of GAS in NSTI, and the exploratory secondary outcome was in- hospital death. A data analysis was conducted using Firth logistic regression adjusted for age, sex, diabetes, and initially affected body region. Results. Overall, 74 NSTI cases were identified, with 49 occurring before, 8 during, and 17 after the pandemic restrictions. GAS was isolated in 27 (36%) cases, with 17 (35%) pre- and 10 (59%) postrestrictions, but none during the restrictions. NSTIs caused by other bacteria persisted during the restrictions. The odds of GAS were significantly lower during the restrictions (adjusted odds ratio, 0.02; 95% CI, 0.001-0.81) compared with after, while no significant differences were found between the pre- and postrestriction periods. Conclusions. The significant decrease of GAS-NSTIs during the COVID-19 pandemic restrictions suggests that isolation measures may have prevented the transmission of GAS, resulting in a decline of GAS-NSTIs while NSTIs caused by bacteria transmitted by alternative routes persisted.