Outbreak of Invasive Group A Streptococcus in Children-Colorado, October 2022-April 2023

Area of Science:

• Microbiology
• Pediatric Infectious Diseases
• Epidemiology

Background:

• Observed a sharp rise in pediatric invasive Group A Streptococcus (iGAS) hospitalizations in Colorado during the fall of 2022.
• Initiated a comparative study of this outbreak against previous years' iGAS epidemiology, clinical features, and patient outcomes.

Purpose of the Study:

• To compare the epidemiology, clinical characteristics, and outcomes of a pediatric invasive Group A Streptococcus (iGAS) outbreak in Colorado during 2022-2023 with historical data.
• To identify potential risk factors and clinical indicators associated with severe iGAS disease in children.

Main Methods:

• Prospectively identified and reviewed 96 iGAS cases in hospitalized pediatric patients from October 2022 to April 2023.
• Retrospectively analyzed sterile site GAS-positive cultures from three periods: pre-COVID-19, pandemic, and outbreak, comparing monthly case counts.

Main Results:

• The outbreak period (9.9 cases/month) showed a nearly threefold increase compared to pre-pandemic levels (3.9 cases/month).
• Associated viral respiratory symptoms were present in nearly 60% of cases. Critical care was required for 39%, with mortality in four patients.
• Outbreak cases had significantly higher rates of pneumonia (28%) and multifocal disease (17%) compared to pre-pandemic and pandemic periods.

Conclusions:

• Invasive Group A Streptococcus (iGAS) outbreak case numbers were almost triple the pre-pandemic baseline.
• The high incidence of associated viral symptoms suggests a link to concurrent respiratory virus surges.
• Early identification of critically ill children may be aided by recognizing specific clinical and laboratory features of severe iGAS.