Post-COVID-19 changes in the epidemiology of group A Streptococcus infections in Taiwan: A retrospective study

BACKGROUND: Temporal changes in group A Streptococcus (GAS) infections have been reported worldwide, but long-term data from Taiwan remain limited. This study evaluated temporal patterns, age-specific disease characteristics, antimicrobial susceptibility, and factors associated with invasive GAS infection. METHODS: We conducted a retrospective study that included patients with GAS infection at a tertiary referral center in Taiwan from 2015 to 2024. Monthly hospital-identified case counts were described, and multivariable logistic regression was used to identify factors associated with invasive disease. RESULTS: Among 454 patients, 33 (7.3%) had invasive disease. Monthly case counts declined markedly during the COVID-19 period (2020-2022), remained low in 2023, and increased to 45 cases in 2024, still below pre-pandemic annual levels. Adults aged ≥65 years accounted for 14 of 33 invasive cases (42.4%). Age ≥18 years (adjusted odds ratio [aOR], 11.6; 95% confidence interval [CI], 4.4-30.9; p < 0.001) and the presence of two or more underlying disease categories (aOR, 29.7; 95% CI, 10.4-84.5; p < 0.001) were associated with invasive disease. All isolates were susceptible to penicillin. Invasive isolates showed higher susceptibility to clindamycin and erythromycin but lower susceptibility to tetracycline than noninvasive isolates. CONCLUSION: Hospital-identified GAS cases showed substantial temporal variation. Older age and greater underlying disease burden were associated with invasive infection. These findings may support clinical risk assessment and institutional surveillance.