In The News: Invasive Group A Strep Data Show Lockdowns Helped Create More Virulent Strain

Medscape reports on research published by Toronto Invasive Bacterial Diseases Network investigators who discovered molecular changes to Group A Streptococcus pyogenes characterized a post-pandemic coinfection surge with respiratory diagnosis. According to experts, the pandemic may have resulted in an immunity deficiency in hosts while simultaneously helping create newly virulent versions of the bacteria.

Over 32 years of pediatric incidence data from southern Ontario, the researchers found invasive Group A Streptococcus pyogenes (iGAS) incidence rate was increasing prior to the pandemic, took a downturn during the pandemic, then had a precipitous post-pandemic rise. This, they report, suggests lockdowns led to a genetic bottleneck of iGAS that triggered adaptive iGAS clones.

Surveillance data for iGAS in pediatric cases during the study period found 498 documented cases of infection. Infection rates rose from 1.8 events per 1,000 population in the 1992-2011 period to 2.4 events per 1,000 population in the 2012-2019 period. Meanwhile, during the pandemic period, rates declined to 1.2 events per 1,000 population in 2020, down further to 0.5 in 2021, only to skyrocket to 6.0 in 2023. Nearly one-third of cases had comorbidities, including soft tissue infection, bacteremia without focus, bone and joint infections, and pneumonia.

Pneumonia occurred more frequently after 2005, while upper respiratory tract infections were more prominent during the 2022-2023 period. In 2023, a spike in iGAS emm1 serotype cases compared to previous years was observed. Aside from a correlation between it and ICU admission, no other associations relating to emm serotypes and disease severity were found.

Post-pandemic iGAS resurgence occurred later in Canada than in population studies from the United Kingdom and the Netherlands. Researchers concluded the study shows the importance of considering age-specific factors in clinical presentation of iGAS infections and highlights the potential of respiratory viral and GAS vaccines to alleviate iGAS infections.

PIDS board member Anthony Flores wrote in an accompanying editorial, “That multiple GAS emm types became more prominent in the post-pandemic iGAS surge, suggests a more complex epidemiological shift than simple clonal expansion. Of note, consistent with [lockdown protocols for] reducing transmission, recent evidence points to decreased antibody levels to major respiratory pathogens during the pandemic supporting an immunity debt that may contribute to many of the described surges in disease. The post-pandemic surges in GAS infections and our lack of understanding of the associated pathogen molecular changes should serve as a clarion call for a renewed emphasis on inactive pathogen surveillance, the study of transmission dynamics, and pathogen emergence.”