Clinical characteristics and exploratory outcome associations among patients hospitalized with acute febrile illness during a post-flood period: a multicenter cohort study from Vietnam.

Flooding can disrupt sanitation, contaminate water sources, and alter patterns of infectious disease; however, causal attribution of an individual febrile illness episode to flood exposure is difficult in retrospective hospital-based data. This study described hospitalized patients with acute febrile illness during a post-flood period in northern Vietnam, exploring associations with adverse short-term outcomes. This multicenter retrospective observational cohort included 237 consecutive patients admitted in Thai Nguyen province from October to November 2025. Demographic, documented environmental, clinical, laboratory, etiologic, and treatment data were obtained from medical records. Severe disease occurred in 8.4% and treatment non-response in 6.8% of patients. At admission, mean high-sensitivity C-reactive protein (hs-CRP) was 103.3 ± 98.3 mg/L, procalcitonin (PCT) was 6.7 ± 11.6 ng/mL, AST was 55.6 ± 61.4 U/L, ALT was 42.5 ± 46.2 U/L, and GGT was 79.9 ± 70.7 U/L. Recorded etiologic diagnoses most commonly included Escherichia coli (33.3%), Vibrio cholerae (18.1%), influenza viruses (13.5%), Leptospira species (11.0%), and Streptococcus pneumoniae (11.0%). Ceftriaxone was administered to 61.5% of patients. Separate univariable exploratory analyses associated severe-flood residence, non-clean water use, chronic disease history, hs-CRP > 100 mg/L, PCT > 2 ng/mL, and fever duration ≥ 3 days with adverse outcomes. These findings represent within-cohort associations among patients from flood-affected communities and do not indicate that flooding caused the illness episodes or outcomes. Most patients exhibited favorable short-term outcomes.