Incidence, aetiology, and enviromental risk factors of community-acquired pneumonia requiring hospitalization in China: a 3-year, prospective, age-stratified, multi-centre case-control study

Qin, Tian; Zhou, Haijian; Ren, Hongyu; Meng, Jiantong; Du, Yinju; Mahemut, Mahemut; Wang, Peng; Luo, Nana; Tian, Fei; Li, Ming; Zhou, Pu; Li, Fang; Duan, Pengyuan; Li, Yinan; Zhao, Na; Yuan, Qiwu; Zhang, Jinzhong; Cheng, Lihong; Luo, Longze; Fang, Ming; Huang, Xin; Gu, Changguo; Zhou, Huifang; Yang, Min; Lu, Shan; Jiang, Xiangkun; Lin, Hualiang; Tian, Huaiyu; Kan, Biao; Xu, Jianguo

BACKGROUND: Community-acquired pneumonia (CAP) is a leading infectious cause of hospitalisation and death worldwide. The knowledge about the incidence and aetiology of CAP in China was fragmented. METHODS: A multicenter study performed at four hospitals in four regions in China and clinical samples from CAP patients were collected and used for pathogen identification from July 2016 to June 2019. RESULTS: A total of 1,674 patients were enrolled and the average annual incidence of hospitalized CAP was 18.7 cases per 10,000 people (95% confidence interval 18.5–19.0). The most common viral and bacterial agents found in patients were respiratory syncytial virus (19.2%) and Streptococcus pneumoniae (9.3%). The co-infections percentage was 13.8%. Pathogen distribution displayed variations within age groups, and seasonal and regional differences. The severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2) was not detected. Respiratory virus detection was significantly positively correlated with air pollutants, including PM(2.5), PM(10), NO(2) and SO(2); and significantly negatively correlated with ambient temperature and O(3) content; bacteria detection was opposite. CONCLUSION: The hospitalized CAP incidence in China was higher than previously known. CAP etiology showed differences in age, seasons, regions, and respiratory viruses were detected at a higher rate than bacterial infection overall. Air pollutants and temperature have influence on the detection of pathogens.