Increased Incidence of Invasive Group A Streptococcus Infections and Fatalities in Southern Wisconsin.

In spring 2024, 2 otherwise healthy men were diagnosed with invasive Group A Streptococcus (iGAS) meningitis at autopsies performed at 2 separate southern Wisconsin (WI) offices. As iGAS is a rare cause of bacterial meningitis, this raised concern for an outbreak and/or increased organism virulence. The 2 offices retrospectively searched their databases for iGAS deaths from 2002 to 2024 and collaborated with the WI State Laboratory of Hygiene (WSLH) and WI Department of Health Services (WI-DHS) to assess corresponding statewide iGAS activity. The search revealed a total of 19 iGAS deaths (age range: 5 to 58 y). More than half of decedents (n=10; 52.6%) had no comorbidities. iGAS variously manifested as bronchopneumonia (26.3%), soft tissue infection (15.8%), epiglottic/retropharyngeal abscess (15.8%), meningitis (10.5%), and sepsis without clear source (31.6%). In 18 cases, the manner of death was natural; 1 death was accidental. The majority of deaths occurred during winter (57.9%) and spring (21.1%). Deaths peaked dramatically in 2023-2024 with almost 1/3 in our series (31.6%) occurring during those 2 years. Concurrently, WSLH and WI-DHS also reported a markedly increased statewide incidence of iGAS diagnosis (948 cases). Reasons for this trend may include postpandemic illness rebound, an aging US population, increasing iGAS virulence, and a lack of a GAS vaccine.