[Clinical characteristics of human adenovirus type 7 pneumonia and genetic characteristics of human adenovirus type 7]

Objective: To better understand the clinical features of human adenovirus type 7 (hAdV7) pneumonia and to identify whether there is a variation in the genome of the strain (CHN/BeiJing/2018) isolated during the small-scale epidemic. Method: Forty-two patients were diagnosed with hAdV7 pneumonia between October 27th, 2017 and February 28th, 2018. They were all males with an average age of (21±2) years. Demographic and clinical data were reviewed and analyzed in detail. The nucleic acid of the epidemic strain was extracted from a bronchoalveolar lavage fluid sample. Whole genome sequencing (WGS) was then performed and sequences were compared with other hAdV7 strains distributed globally. Phylogenetic tree analysis was conducted based on whole genome sequences of the epidemic strain. Results: Thirty-eight cases with hAdV7 pneumonia presented with influenza-like symptoms (90.5%) at the onset and 36 cases developed fever (85.7%), followed by cough (97.6%), expectoration (90.5%) and chest pain (28.6%). Five cases presented with tonsillitis(11.9%) and 4 had transient hemoptysis (9.5%), while 3 patients reported dyspnea (7.1%). Moist rales were only heard in 3 patients (7.1%). Notably elevated creatine kinase (CK) concentrations were observed in 8 patients (19.1%), but all returned to normal after treatment. Four cases developed hypoxemia (9.5%), but none of them progressed to respiratory failure or acute respiratory distress syndrome (ARDS). Chest CT imaging showed bilateral patchy parenchymal opacities with a random distribution with or without consolidation. Ten patients were co-infected with influenza virus (23.8%), while 32 patients developed atypical pneumonia (76.2%). Genomic analysis revealed that the strain isolated during this epidemic was 99% similar to the known hAdV7 strains (19BOVLB/Volgograd/Rus/2014 and 0901HZ/ShX/CHN/2009). Phylogenetic tree analysis suggested that the strain was closely related to the hAdV7 strain isolated in Jingmen China in 2012. Conclusions: Cases with hAdV7 pneumonia were generally mild. Symptomatic treatment was sufficient for a favorable prognosis. A good genome stability of the hAdV7 strain was observed, indicating that hAdV7 could remain stable for a long period and cause continuing sporadic cases and clusters.