A Fall 2022 Surge in Invasive Group A Strep Among Children in Colorado and Minnesota

In fall 2022, two of CDC's Emerging Infections Program surveillance sites — Colorado (the Denver area) and Minnesota (the whole state) — saw a resurgence of invasive group A Streptococcus (iGAS) infection in children and adolescents. It followed historic declines in invasive bacterial disease in 2020, during COVID-19 mitigation, and came earlier than usual seasonal rises, alongside a return of hospitalizations for RSV and influenza. Viral infections such as flu and chickenpox are known risk factors for iGAS — and vaccines can prevent them.

The comparison

Cases in residents under 18 were compared across three periods using Active Bacterial Core surveillance data.

• Colorado patients were younger in 2022 (median 3.1 years, against 5.6 at baseline and 6.2 in the pandemic); Minnesota's weren't.
• Two children died in the 2022 period (one in each state); five had died in 2016–2021.
• Intensive care (35.3%) and length of stay (4.5 days) were similar to baseline (34.4%, 5.0 days).
• 25 of 34 (73.5%) had no underlying conditions.

Pediatric iGAS cases, with influenza and RSV hospitalization rates, in Colorado and Minnesota, January 2016–December 2022. Figure from CDC's report.

Viruses first

• 21 of the 34 had an upper respiratory infection in the 2 weeks before, 6 a sore throat, and 7 no preceding illness.
• 15 tested positive for a respiratory virus before or with their iGAS: RSV (6), influenza (6) and SARS-CoV-2 (3).
• In most years, iGAS rose with the seasonal peaks of RSV and flu hospitalizations — except 2021, when those were low.

The bacteria

Of 26 isolates typed, 22 were emm type 1 (9) or type 12 (13) — also the two commonest at baseline. Genome sequencing showed no change in predicted antibiotic susceptibility and no single spreading clone: 23 were susceptible to all antibiotics; one type 12 was resistant to erythromycin, and two type 77 to erythromycin, clindamycin and tetracycline.

What it means

More respiratory viruses, plus less exposure to group A strep — and so less immunity to common types — during the pandemic may have left children more vulnerable once restrictions lifted. The share with flu suggests flu vaccination might lower iGAS risk, as chickenpox vaccination has been shown to.

Clinicians should consider iGAS as a cause of severe illness in children and adults — especially those at higher risk: people 65 and older, American Indian or Alaska Native people, long-term care residents, people with diabetes, cancer, weakened immunity, or kidney, heart or lung disease, people with wounds or skin disease, and people who inject drugs or are homeless — and offer flu and chickenpox vaccines to those not up to date.

Sources

Based on Barnes M, Youngkin E, Zipprich J, et al., "Notes from the Field: Increase in Pediatric Invasive Group A Streptococcus Infections — Colorado and Minnesota, October–December 2022," MMWR Morbidity and Mortality Weekly Report, volume 72, Centers for Disease Control and Prevention; a work of the United States government in the public domain.