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

In the fall of 2022, we observed a sharp rise in pediatric Invasive Group A Streptococcus (iGAS) hospitalizations in Colorado. We compared the epidemiology, clinical features, and patient outcomes in this outbreak to prior years.

Between October 2022 and April 2023, we prospectively identified and reviewed iGAS cases in hospitalized pediatric patients at Children's Hospital Colorado. Using laboratory specimen records, we also retrospectively compared the number of patients with sterile site GAS-positive cultures across three time periods: pre-COVID-19 (January 2015-March 2020), height of COVID-19 pandemic (April 2020-September 2022), and outbreak (October 2022-April 2023).

Among 96 prospectively identified iGAS cases, median age was 5.7 years old; 66% were male, 70% previously healthy, 39% required critical care, and four patients died. Almost 60% had associated respiratory viral symptoms, 10% had toxic shock syndrome, and 4% had necrotizing fasciitis. Leukopenia, bandemia, and higher C-reactive protein values were laboratory findings associated with need for critical care. There were significantly more cases during the outbreak (9.9/month outbreak vs 3.9/month pre-pandemic vs 1.3/month pandemic), including more cases with pneumonia (28% outbreak vs 15% pre-pandemic vs 0% pandemic) and multifocal disease (17% outbreak vs 3% pre-pandemic vs 0% pandemic), P < .001 for all.

Outbreak case numbers were almost triple the pre-pandemic baseline. The high percentage of cases with associated viral symptoms suggests a link to coinciding surges in respiratory viruses during this time. Invasive GAS can be severe and evolve rapidly; clinical and laboratory features may help in earlier identification of critically ill children.