Casual effects of gut microbiota on the severity of COVID-19: a two-sample Mendelian randomization and a meta-analysisAimin Jiang1†, Zheng Wang1†, Demeng Xia2†, Peng Luo3, Xinxin Gan1, Renqi Yao4,5*, Linhui Wang1*1 Department of Urology, Changhai Hospital, Naval Medical University, Shanghai 200433, China2 Department of Orthopedics, Changhai Hospital, Naval Medical University, Shanghai, China3 Department of Oncology, Zhujiang Hospital, Southern Medical University, Guangzhou 510260, China.4 Translational Medicine Research Center, Fourth Medical Center and Medical Innovation Research Division of the Chinese PLA General Hospital, Beijing 100048, China5 Department of Burn Surgery, Changhai Hospital, Naval Medical University, Shanghai 200433, China† Aimin Jiang, Zheng Wang, and Demeng Xia contributed equally to this work.Correspondence:Linhui Wang, MD, PhD, Department of Urology, Changhai Hospital, No.168 Road, Yangpu District, Shanghai 200433, People’s Republic of China. Tel: (+86) 13901635510; Email:[email protected] Yao, MD, Translational Medicine Research Center, Medical Innovation Research Division and Fourth Medical Center of the Chinese PLA General Hospital, 28 Fuxing Road, Haidian District, Beijing 100853, People’s Republic of China. Tel: (+86) 18501689629; Email:[email protected]:Mendelian randomization, SARS-CoV-2, COVID-19, gut microbiota, infection