2022–2023 United States group A streptococcus outbreak

The Streptococcus pyogenes (Strep A) outbreak in the U.S. intensified in late 2022, with significant increases noted starting in October 2022, particularly in Colorado and Minnesota, affecting children and adolescents with invasive infections, with spikes continuing into early 2023.^[1]

The U.S. Centers for Disease Control and Prevention (CDC) reported that rates of serious GAS disease had been increasing since 2014, but the number of serious GAS infections reached a 20-year high in 2023. According to the CDC, there were between 20,000 and 27,000 cases of iGAS per year in the U.S. 5 years before, resulting in approximately 2,000 deaths each year. ^[2]

During the 2022-2023 flu season, there was a "tripledemic" (COVID-19, flu, RSV) surge, combined with pandemic-era reduced exposure, likely fueled a rise in invasive Group A Strep (iGAS) infections by creating immunity gaps and increasing viral coinfections that predispose people to severe strep, leading to more virulent strains and heightened infection rates post-pandemic. ^[3] From January 2017 through February 2020, strep throat infections followed a seasonal pattern, typically starting to increase in September and peaking at between 0.63 and 0.74% of encounters in February each year. Similar to other infectious respiratory illnesses like influenza and RSV, strep throat encounters dramatically decreased in March 2020, coinciding with the start of the COVID-19 pandemic. Rates remained low (less than 0.28% of encounters) but began to rise again in September 2022. As of February 2023, strep throat encounters increased to a rate nearly 30% greater than the previous peak seen in February 2017 (0.74% to 1.0% of encounters). ^[4]

This rise occurred as typical seasonal patterns returned, peaking from December to April, coinciding with high respiratory virus circulation.^[5]

• 2022-2023 United Kingdom group a streptococcus outbreak
• Streptococcal pharyngitis