OBJECTIVE  To explore the risk factors for severe influenza patients in Fuzhou, and to provide reference for the prevention and control of severe influenza.

METHODS  Information on 412 patients with severe influenza in Fuzhou City with onset dates from Jan. 2023 to Jan. 2025 was collected from the China Influenza Surveillance Information System and the China Disease Prevention and Control Information System. The severe patients were matched 1∶1 with non-severe patients based on gender and age ± 3 years of the severe patients. Basic information, vaccination history, clinical symptoms, types of infecting viruses and medical history of both groups of patients were collected to summarize the risk factors for severe illness progression in influenza patients.

RESULTS  The proportions of obesity, retired personnel, children or students, unemployed individuals and smokers in the severe group were all higher than those in the non-severe group, while the vaccination rate (6.07%) was lower than that of the non-severe group (16.50%) (P < 0.001). The proportions of typical symptoms of shortness of breath/dyspnea and altered mental status/convulsions in the severe group were 23.30% and 21.60%, respectively, which were higher than those in the non-severe group (P < 0.001). The proportions of individuals with a history of chronic respiratory diseases and cancer/tumors in the severe group were 26.70% and 19.90%, respectively, which were higher than those in the non-severe group (P < 0.001). The proportion of influenza A (H1N1) in the severe group (58.50%) was higher than that in the non-severe group (39.32%) (P < 0.001). Retired personnel, children or students and unemployed individuals were high-risk groups for the severe influenza, while farmers were a low-risk group. Obesity (OR=1.966), unvaccination (OR=3.738), smoking (OR=1.787), typical symptoms of shortness of breath/dyspnea (OR=3.305), altered mental status/convulsions (OR=4.099), history of chronic respiratory diseases (OR=4.820) and history of cancer/tumors (OR=3.269) and infection with influenza A (H1N1) (OR=6.422) and influenza A (H3N2) (OR=4.441) were risk factors for the severe influenza (P < 0.05). The recovery time in the severe group was 21 (6, 33) days, which was longer than that in the non-severe group (P < 0.001).

CONCLUSIONS  Obesity, unvaccination, smoking, typical symptoms of shortness of breath/dyspnea, altered mental status/convulsions, history of chronic respiratory diseases and history of cancer/tumors and infection with influenza A (H1N1) and influenza A (H3N2) are risk factors for severe influenza patients. It is necessary to strengthen influenza prevention and control among the elderly and children, enhance health education, and continuously promote influenza vaccination among key populations.