Infectious Disease · Medical Literature
[Comment] From paediatric rebound to adult redistribution: changing the epidemiology of group A Streptococcus after COVID-19
Abstract
The post-pandemic epidemiology of Streptococcus pyogenes has largely been interpreted through the lens of the 2022–23 upsurge, when the incidence of scarlet fever and invasive group A Streptococcus (iGAS), increased across several European countries, particularly among children. However, the mechanisms underlying this resurgence remain only partially resolved and likely reflect the convergence of altered host susceptibility, viral co-circulation, and microbiome dynamics rather than a single explanatory pathway.
Clinical relevance
Has the post-COVID-19 epidemiological pattern of group A Streptococcus (GAS) infections shifted beyond the well-documented 2022–23 paediatric upsurge, and if so, toward which age group and infection categories? __SNAPSHOT__ {"studyDesign":"Observational, microbiology-based epidemiological commentary/correspondence with extended institutional surveillance data (single-centre temporal analysis); not a primary interventional or analytic cohort study","setting":"Single Italian tertiary hospital (Fondazione Policlinico Universitario A. Gemelli IRCCS, Rome, Italy)","sampleSize":"Not reported (aggregate institutional surveillance data across respiratory [rGAS], invasive [iGAS], and other [oGAS] GAS infection categories, 2022–2025)","population":"All-age patients with laboratory-confirmed GAS infections presenting to a large Italian tertiary referral centre during the post-pandemic period (2022–2025), encompassing paediatric and adult age groups","intervention":"Extended prospective surveillance through 2024–2025 to characterise temporal and age-based redistribution of GAS infection burden","comparator":"Pre-pandemic and 2022–23 upsurge periods used as historical internal comparators; no concurrent external control group","primaryOutcome":"Age-group distribution (paediatric vs. adult) and infection-category distribution (rGAS, iGAS, oGAS) of GAS cases over time, with particular attention to whether the paediatric-predominant signal of 2022–23 persisted or shifted","followUp":"Approximately 2022–2025 (multi-year institutional surveillance); exact dates not precisely delineated in the abstract","fundingSource":"Not reported in the provided abstract; a prior related publication from the same group acknowledged EU/MUR PNRR funding (Project INF-ACT, PE00000007)"}
Key findings
The authors report that, contrary to the expectation of a sustained paediatric-driven epidemic, extending institutional GAS surveillance through 2024–2025 revealed a progressive redistribution of GAS disease burden away from children and toward adults. The 2023 data had confirmed a marked paediatric rebound—particularly among preschool-aged children—consistent with the immunity debt hypothesis following relaxation of non-pharmaceutical interventions (NPIs). However, 2024 showed a 'mixed profile,' and by 2025, a clear shift toward adult predominance was observed across all three infection categories: respiratory GAS (rGAS), invasive GAS (iGAS), and other GAS (oGAS), accompanied by contraction of the paediatric signal seen in 2023. No quantitative incidence rates, relative risks, confidence intervals, odds ratios, or p-values are reported in the available abstract. The study acknowledges that immunological data—specifically, reduced antibody responses in young children following NPI exposure—support the delayed immunity acquisition framework that may explain the preschool peak in 2023, but that immunity alone is unlikely to account for observed temporal dynamics; microbiome-mediated susceptibility may also contribute. All effect sizes and absolute case numbers are not reported.
Practice implications
This commentary, based only on a single tertiary centre's surveillance data, establishes that the epidemiological trajectory of GAS infections in the post-COVID-19 era is dynamic and does not conform to a simple, persistent paediatric epidemic model. The 2022–23 paediatric upsurge appears to have represented a transient susceptibility gap rather than an enduring structural shift in GAS epidemiology. By 2025, the adult population had emerged as the predominant group across respiratory, invasive, and other GAS infection categories at this institution. These findings carry clinical relevance for adult-facing clinicians who may underestimate GAS risk in their patient populations. However, the study's interpretation is substantially constrained: it is a single-centre institutional commentary with no external validation, no statistical comparisons reported, no population-level incidence denominators, and is available only as an abstract/correspondence. The mechanistic explanations offered (immunity debt, microbiome dynamics, viral co-circulation) remain hypotheses not directly tested in this study. The findings cannot be presumed generalisable beyond the Italian tertiary hospital setting, and the extent to which this age redistribution reflects true epidemiological change versus healthcare-seeking behaviour, surveillance intensity, or referral patterns remains uncertain. Practice should not change based on this commentary alone, but clinicians should maintain heightened awareness of GAS in adult patients and advocate for age-stratified, integrated surveillance systems. __LIMITATIONS__ Single-centre design from one Italian tertiary referral hospital limits generalisability; referral bias and healthcare-seeking patterns may confound age-group distributions.,Correspondence/commentary format: only an abstract is publicly available; full data, methods, statistical analyses, and case-level details cannot be independently evaluated.,No quantitative effect measures (incidence rates, rate ratios, confidence intervals, p-values) are reported, precluding assessment of statistical significance or precision.,Hospital-based microbiology datasets likely underestimate total community GAS burden, particularly mild and non-invasive disease; authors acknowledge this limitation explicitly.,Absence of population-level denominators makes it impossible to determine whether adult predominance in 2025 reflects increased incidence or shifts in care-seeking or testing practices.,Mechanistic hypotheses (immunity debt, microbiome dynamics, viral co-circulation) are not directly tested in this study and remain speculative.,No genomic or strain-typing data are presented in this report, so the contribution of hypervirulent clones (e.g., M1UK) to the adult shift cannot be assessed.,Funding source and potential conflicts of interest are not disclosed in the abstract. __BOTTOM_LINE_CATEGORY__ promising_but_preliminary __BOTTOM_LINE__ This single-centre Italian surveillance commentary suggests that the post-COVID-19 GAS epidemic has evolved from a paediatric-predominant rebound in 2022–23 to adult predominance across respiratory, invasive, and other GAS infection categories by 2025, warranting increased clinical vigilance for GAS in adult patients. However, the absence of quantitative data, the single-centre design, and the commentary format mean these findings are hypothesis-generating rather than definitive. Clinicians should monitor forthcoming multi-centre and population-level surveillance data before making substantive changes to clinical practice or age-targeted screening protocols.