More than 3,000 people in England were affected by Strep A between September 2022 and May 2023

A new analysis led by the UK Health Security Agency (UKHSA) and Imperial College London (ICL) has confirmed that a variant called M1UK played a key role in the global increase of group A Streptococcus (Strep A) infections.

The research was supported by the National Institute for Health and Care Research (NICE), the UKRI Medical Research Council and the NIHR Imperial Biomedical Research Centre.

Affecting more than 3,000 people in England between September 2022 and May 2023, according to the UKHSA, Strep A is a common form of bacteria that, in rare cases, can cause invasive infections.

During this time, global health agencies recorded a surge in severe invasive Step A infections following the lifting of the COVID-19 pandemic restrictions.

M1 strains are known to cause invasive infections more than other types of Strep A and have been recently linked to the rise in the number of severe infections in Europe, Australia, North America and Japan.

Carried out with the NIHR Health Protection Research Unit in Healthcare-Associated Infections and Antimicrobial Resistance, scientists looked into the genetics of M1UK, provided new insights into its first emergence and compared it to other strains.

Using genetic sequencing of samples obtained from patients combined with computer modelling, researchers revealed that M1UK first emerged around 2008 before significantly progressing from 2010 onwards.

The analysis revealed that genetic features of M1UK could more easily spread compared to other strains and have the potential to cause more severe disease despite reduced Strep A during the pandemic, waning immunity in the population.

Researchers suggest that the increasing population immunity to the M1UK strain could enable other strain types to emerge.

Shiranee Sriskandan, clinical director, Centre for Bacterial Resistance Biology, ICL, commented: “The surges we are seeing at different times worldwide are likely due to reduced immunity against specific respiratory pathogens, especially Strep A” and “vaccines could help to prevent this”.