Oral Presentation Lancefield International Symposium for Streptococci and Streptococcal Diseases 2025

Incidence of invasive group A streptococcal infections and comparison of emm types from carriage, pharyngitis, and invasive infections in Indigenous communities in the Southwest United States (116858)

Catherine Sutcliffe 1 , Victoria Sergent 1 , Joyselynn Pitalua 1 , Sopio Chochua 2 , Chris Gregory 2 , Chloe Hurley 1 , Zhongya Li 3 , Saundra Mathis 3 , Lesley McGee 2 , Jennifer Okaro 2 , Theresa Tran 2 , Robert Weatherholtz 1 , Laura L Hammitt 1
  1. Center for Indigenous Health, Johns Hopkins Bloomberg School of Public Health, Baltimore, MD, United States
  2. Division of Bacterial Diseases, Centers for Disease Control and Prevention, Atlanta, Georgia, United States
  3. ASRT Inc, Contractor to Pneumonia and Streptococcus Laboratory Branch, Centers for Disease Control and Prevention, Atlanta, Georgia, United States

Background

Indigenous communities are disproportionately affected by group A Streptococcus (GAS) infections. We determined the incidence of invasive infections in two Indigenous communities in the U.S. and compared emm types from carriage, pharyngitis, and invasive infections.

Methods

Study activities included: laboratory-based surveillance for invasive GAS infections in White Mountain Apache Tribal lands (WMAT) (2017–2024) and Navajo Nation (NN) (2023–2024); GAS culture of pediatric oropharyngeal carriage samples (2022–2023); and laboratory-based surveillance for pediatric GAS pharyngitis (2023–2024). Emm types were determined by sequencing. We calculated coverage with a 30-valent vaccine in development.

Results

In WMAT, age-standardized rates of invasive infections were 114–270/100,000 in 2017–2020 and 80–99/100,000 in 2021–2024. Predominant emm types varied: 82 predominated in 2017 (67% of isolates), 91 (59%) and 49 (32%) in 2019–2020, and 43 (40%) and 53 (30%) in 2023. In NN, rates were 40–58/100,000 in 2023–2024; common emm types were 53 (28%), 101 (18%), and 12 (16%). Emm types 1, 12, and 53 predominated in pharyngitis, and 1, 12, and 91 in carriage. The percentage of emm types included in the 30-valent vaccine was higher for carriage (86%/72% in WMAT/NN) and pharyngitis (78%/86%) than invasive infections (50%/43%).

Conclusions

Incidence of invasive GAS in these communities was 5–40 times higher than national U.S. estimates (8.2/100,000 in 2022). Emm types varied over time with limited overlap in strains causing carriage/pharyngitis and invasive infections. Findings support expanding GAS surveillance and engaging Indigenous communities during vaccine development and evaluation.