Increase in invasive group A streptococcal infections and emergence of novel, rapidly expanding sub-lineage of the virulent Streptococcus pyogenes M1 clone, Denmark, 2023
Thor Bech Johannesen, Charlotte Munkstrup, Sofie Marie Edslev, Sharmin Baig, Stine Nielsen, Tjede Funk, Dennis Karsten Kristensen, Lars Hervig Jacobsen, Signe Fischer Ravn, Niels Bindslev, Sophie Gubbels, Marianne Voldstedlund, Pikka Jokelainen, Søren Hallstrøm, Astrid Rasmussen, Karl G. Kristinsson, David Fuglsang-Damgaard, Ram Benny Dessau, Agnieszka Barbara Olsén, Christian S. Jensen, Annette Skovby, Svend Ellermann‐Eriksen, Thøger Gorm Jensen, Esad Dzajic, Claus Østergaard, Steen Lomborg Andersen, Steen Hoffmann, Peter Henrik Andersen, Marc Stegger
Abstract
A highly virulent sub-lineage of the Streptococcus pyogenes M1 clone has been rapidly expanding throughout Denmark since late 2022 and now accounts for 30% of the new invasive group A streptococcal infections. We aimed to investigate whether a shift in variant composition can account for the high incidence rates observed over winter 2022/23, or if these are better explained by the impact of COVID-19-related restrictions on population immunity and carriage of group A Streptococcus .