Cervical Necrotizing Fasciitis Across the COVID-19 Pandemic: A Single-Center Exploratory Retrospective Cohort Study

Background/Objectives: Cervical necrotizing fasciitis (CNF) is a rare but rapidly progressive deep-neck infection. Reports suggest a rising incidence after the COVID-19 pandemic, but host-response biomarkers remain poorly characterized. We evaluated whether the pandemic/post-pandemic era was associated with higher CNF frequency and a distinct immunonutritional profile. Methods: Retrospective cohort at a Croatian national tertiary referral center. Adults with CNF were grouped by admission era: pre-pandemic (2010–2019; n = 11; 10.00 years) and pandemic/post-pandemic (January 2021–April 2026; n = 15; 5.29 years). Incidence was compared by Poisson rate ratio (IRR). Admission biomarkers included classical indices (NLR, PLR, LMR, SII, AISI) and albumin-integrated composites (CAR, NAR, NPAR, PNI, CALLY, CAR/PNI, SIRI/albumin, AISI/albumin). Mann–Whitney U and Fisher’s exact tests were used with the Benjamini–Hochberg FDR correction; ROC analysis with bootstrap 95% CIs assessed era discrimination. Results: Incidence rose 2.6-fold (IRR = 2.58; 95% CI 1.18–5.61; p = 0.021); sensitivity analysis excluding 2026 was consistent (IRR = 2.36; p = 0.048). All 21 odontogenic cases originated from mandibular culprit teeth. Comorbidities (27% vs. 67%) and complications (27% vs. 53%) were more frequent in the pandemic/post-pandemic era, while overall mortality was 11.5%. Among the evaluated biomarkers, NPAR (q = 0.030) and CAR/PNI (q = 0.030) showed the strongest discriminatory performance for era classification (AUC 0.867 and 0.855, respectively) within this exploratory cohort. Streptococci fell from 82% to 33% (p = 0.021); S. pyogenes disappeared, S. anginosus/constellatus persisted, and atypical organisms (Acinetobacter, Candida, Corynebacterium) emerged exclusively post-pandemic (0% vs. 20%). Conclusions: Pandemic/post-pandemic CNF was more frequent, more comorbid, and biologically distinct, with a coherent hypoalbuminemic hyperinflammatory profile with diversified microbiology. In this single-center cohort, these associations are exploratory and hypothesis-generating, and the era label denotes a calendar period rather than a confirmed individual SARS-CoV-2 infection. NPAR and CAR/PNI emerged as the most promising exploratory biomarkers and warrant prospective multicenter validation.