Objective
The H7N9 avian influenza virus, identified in China in 2013, has posed a significant threat to public health due to its high mortality rate. This systematic review aims to evaluate the clinical characteristics and mortality risk factors of H7N9 patients.

Methods
English and Chinese databases (PubMed, Web of Science, Embase, CNKI, VIP, Wanfang) were searched for studies on laboratory-confirmed H7N9 cases with available data on symptom onset, diagnosis time, clinical features, oseltamivir administration, and outcomes. Univariate and multivariate analyses were performed on the pooled case data to assess the relationship between clinical factors and mortality risk.

Results
A total of 166 studies including 237 H7N9 cases were analyzed, with an overall mortality rate of 41.77%. Univariate analysis showed higher mortality in patients with advanced age?≥?66 years (62.50%), those with underlying diseases (60.20%), those who received oseltamivir?≥?8 days after symptom onset (54.17%), and those diagnosed?≥?11 days after onset (62.75%), whereas patients treated with oseltamivir within 2 days of onset had the lowest mortality (17.39%). Multivariate analysis identified advanced age?≥?66 years (OR?=?3.10, 95% CI: 1.07–8.99, P?=?0.037) and delayed oseltamivir administration after symptom onset (OR?=?4.63, 95% CI: 1.12–19.18, P?=?0.034) as independent predictors of mortality, while sex, underlying diseases, and onset-to-diagnosis time were not statistically significant.

Conclusion
Older age and delayed initiation of oseltamivir are key independent predictors of mortality in H7N9 infection. Prompt diagnosis is crucial to facilitate early antiviral treatment, which may improve survival. Future prospective studies are needed to validate these findings and optimize clinical management.