Jianxin Ma, Xiao Qi, Haoxuan Chen, Xinyue Li, Zheng Zhang, Haibin Wang, Lingli Sun, Lu Zhang, Jiazhen Guo, Lidia Morawska, Sergey A Grinshpun, Pratim Biswas, Richard C Flagan, Maosheng Yao*，Coronavirus Disease 2019 Patients in Earlier Stages Exhaled Millions of Severe Acute Respiratory Syndrome Coronavirus 2 Per Hour, Clinical Infectious Diseases, ciaa1283. DOI: 10.1093/cid/ciaa1283.