Increasing Incidence of Invasive Group A Streptococcus Disease, Idaho, USA, 2008–2019

We investigated invasive group A Streptococcus epidemiology in Idaho, USA, during 2008–2019 using surveillance data, medical record review, and emm (M protein gene) typing results. Incidence increased from 1.04 to 4.76 cases/100,000 persons during 2008–2019. emm 1, 12, 28, 11, and 4 were the most common types, and 2 outbreaks were identified. We examined changes in distribution of clinical syndrome, patient demographics, and risk factors by comparing 2008–2013 baseline with 2014–2019 data. Incidence was higher among all age groups during 2014–2019. Streptococcal toxic shock syndrome increased from 0% to 6.4% of cases (p = 0.02). We identified no differences in distribution of demographic or risk factors between periods. Results indicated that invasive group A Streptococcus is increasing among the general population of Idaho. Ongoing surveillance of state-level invasive group A Streptococcus cases could help identify outbreaks, track regional trends in incidence, and monitor circulating emm types.