Rapid communication Open Access
Like 0


A highly virulent sub-lineage of the 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 .


Article metrics loading...

Loading full text...

Full text loading...



  1. Guy R, Henderson KL, Coelho J, Hughes H, Mason EL, Gerver SM, et al. Increase in invasive group A streptococcal infection notifications, England, 2022. Euro Surveill. 2023;28(1):2200942.  https://doi.org/10.2807/1560-7917.ES.2023.28.1.2200942  PMID: 36695450 
  2. de Gier B, Marchal N, de Beer-Schuurman I, Te Wierik M, Hooiveld M, de Melker HE, et al. Increase in invasive group A streptococcal (Streptococcus pyogenes) infections (iGAS) in young children in the Netherlands, 2022. Euro Surveill. 2023;28(1):2200941.  https://doi.org/10.2807/1560-7917.ES.2023.28.1.2200941  PMID: 36695447 
  3. World Health Organization Regional Office for Europe (WHO/Europe). Increase in invasive Group A streptococcal infections among children in Europe, including fatalities.  Copenhagen: WHO/Europe; 2022. Available from: https://www.who.int/europe/news/item/12-12-2022-increase-in-invasive-group-a-streptococcal-infections-among-children-in-europe--including-fatalities
  4. Voldstedlund M, Haarh M, Mølbak K, MiBa Board of Representatives. The Danish Microbiology Database (MiBa) 2010 to 2013. Euro Surveill. 2014;19(1):20667.  https://doi.org/10.2807/1560-7917.ES2014.19.1.20667  PMID: 24434175 
  5. Statistics Denmark (DST). Population figures. Copenhagen: DST. [Accessed: 8 Jun 2023]. Available from: https://www.dst.dk/
  6. Wang Y, Zhao Y, Bollas A, Wang Y, Au KF. Nanopore sequencing technology, bioinformatics and applications. Nat Biotechnol. 2021;39(11):1348-65.  https://doi.org/10.1038/s41587-021-01108-x  PMID: 34750572 
  7. Lynskey NN, Jauneikaite E, Li HK, Zhi X, Turner CE, Mosavie M, et al. Emergence of dominant toxigenic M1T1 Streptococcus pyogenes clone during increased scarlet fever activity in England: a population-based molecular epidemiological study. Lancet Infect Dis. 2019;19(11):1209-18.  https://doi.org/10.1016/S1473-3099(19)30446-3  PMID: 31519541 
  8. Davies MR, Keller N, Brouwer S, Jespersen MG, Cork AJ, Hayes AJ, et al. Detection of Streptococcus pyogenes M1UK in Australia and characterization of the mutation driving enhanced expression of superantigen SpeA. Nat Commun. 2023;14(1):1051.  https://doi.org/10.1038/s41467-023-36717-4  PMID: 36828918 
  9. Schmidt M, Schmidt SAJ, Sandegaard JL, Ehrenstein V, Pedersen L, Sørensen HT. The Danish National Patient Registry: a review of content, data quality, and research potential. Clin Epidemiol. 2015;7:449-90.  https://doi.org/10.2147/CLEP.S91125 
  10. R Core Team. R: A language and environment for statistical computing. Vienna: R Foundation for Statistical Computing; 2020. Available from: https://www.R-project.org
  11. Kachroo P, Eraso JM, Beres SB, Olsen RJ, Zhu L, Nasser W, et al. Integrated analysis of population genomics, transcriptomics and virulence provides novel insights into Streptococcus pyogenes pathogenesis. Nat Genet. 2019;51(3):548-59.  https://doi.org/10.1038/s41588-018-0343-1  PMID: 30778225 
  12. Barnett TC, Bowen AC, Carapetis JR. The fall and rise of Group A Streptococcus diseases. Epidemiol Infect. 2018;147:e4.  https://doi.org/10.1017/S0950268818002285  PMID: 30109840 
  13. Brouwer S, Barnett TC, Ly D, Kasper KJ, De Oliveira DMP, Rivera-Hernandez T, et al. Prophage exotoxins enhance colonization fitness in epidemic scarlet fever-causing Streptococcus pyogenes. Nat Commun. 2020;11(1):5018.  https://doi.org/10.1038/s41467-020-18700-5  PMID: 33024089 
  14. van der Putten BCL, Vlaminckx BJM, de Gier B, Freudenburg-de Graaf W, van Sorge NM. Group A streptococcal meningitis with the M1UK variant in the Netherlands. JAMA. 2023;329(20):1791-2.  https://doi.org/10.1001/jama.2023.5927  PMID: 37027150 
  15. Alcolea-Medina A, Snell LB, Alder C, Charalampous T, Williams TGS, Tan MKI, et al. The ongoing Streptococcus pyogenes (Group A Streptococcus) outbreak in London, United Kingdom, in December 2022: a molecular epidemiology study. Clin Microbiol Infect. 2023;29(7):887-90.  https://doi.org/10.1016/j.cmi.2023.03.001  PMID: 36925107 

Data & Media loading...

Supplementary data

Submit comment
Comment moderation successfully completed
This is a required field
Please enter a valid email address
Approval was a Success
Invalid data
An Error Occurred
Approval was partially successful, following selected items could not be processed due to error