Objective As coronavirus disease 2019 (COVID‐19) crashed into the influenza season, clinical characteristics of both infectious diseases were compared to make a difference. Methods We reported 211 COVID‐19 patients and 115 influenza patients as two separate cohorts at different locations. Demographic data, medical history, laboratory findings, and radiological characters were summarized and compared between two cohorts, as well as between patients at the Intensive Care Unit (ICU) and non‐ICU within the COVID‐19 cohort. Results For all 326 patients, the median age was 57.0 (IQR 45.0‐69.0) and 48.2% was male, while 43.9% had comorbidities that included hypertension, diabetes, bronchitis, and heart diseases. Patients had cough (75.5%), fever (69.3%), expectoration (41.1%), dyspnea (19.3%), chest pain (18.7%) and fatigue (16.0%), etc. Both viral infections caused substantial blood abnormality, whereas the COVID‐19 cohort showed a lower frequency of leukocytosis, neutrophilia or lymphocytopenia, but a higher chance of creatine kinase elevation. 7.7% of all patients possessed no abnormal sign in chest CT scans. For both infections, pulmonary lesions in radiological findings did not show any difference in their location or distribution. Nevertheless, compared to the influenza cohort, the COVID‐19 cohort presented more diversity in CT features, where certain specific CT patterns showed significantly more frequency, including consolidation, crazy paving pattern, rounded opacities, air bronchogram, tree‐in‐bud sign, interlobular septal thickening, and bronchiolar wall thickening. Conclusion Differentiable clinical manifestations and CT patterns may help diagnose COVID‐19 from influenza and gain a better understanding of both contagious respiratory illnesses. This article is protected by copyright. All rights reserved.

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Exosomes derived from human umbilical cord mesenchymal stem cells (hucMSC-ex) are nano-sized membrane-bound vesicles that have been reported to facilitate skin regeneration and repair. However, the roles played by hucMSC-ex in ultraviolet (UV) radiation-induced skin photodamage and the underlying mechanisms remain unknown. To investigate the functions of hucMSC-ex in a rat model of acute skin photodamage, immunofluorescence and immunohistochemical staining, quantitative real-time-polymerase chain reaction (qRT-PCR), western blot, and gene silencing assays were performed. We found that the in vivo subcutaneous injection of hucMSC-ex elicited antioxidant and anti-inflammatory effects against UV radiation-induced DNA damage and apoptosis. Further studies showed that the sirtuin 1 (SIRT1) expression level in skin keratinocytes (HaCaT) decreased in a time- and dose-dependent manner under in vitro UV radiation induced-oxidative stress conditions, which could be reversed by treatment with hucMSC-ex. The activation of SIRT1 significantly attenuated UV- and H 2 O 2 -induced cytotoxic damage by inhibiting oxidative stress and promoting the activation of autophagy. Our study found that 14-3-3ζ protein, which was delivered by hucMSC-ex, exerted a cytoprotective function via the modulation of a SIRT1-dependent antioxidant pathway. Collectively, our findings indicated that hucMSC-ex might represent a new potential agent for preventing or treating UV radiation-induced skin photodamage and aging.