Yuen Kwok-yung (; born 30 December 1956) is a Hong Kong microbiologist, physician and surgeon. He is a prolific researcher, with most of his nearly 800 papers (as of December 2020) related to research on novel microbes or emerging infectious diseases. He led a team identifying the SARS coronavirus that caused the SARS pandemic of 2003–4, and traced its genetic origins to wild bats. During the ongoing COVID-19 pandemic, he has acted as expert adviser to the Hong Kong government. Career Yuen graduated from the Faculty of Medicine at the University of Hong Kong in 1981 with distinction in Medicine. Initially trained as a surgeon, he switched successfully to a physician and, subsequently, a clinical microbiologist. He worked at the United Christian Hospital, and after 6 years service, left to join a research team at the Queen Mary Hospital. In the outbreak of avian influenza virus H5N1 in 1997 in Hong Kong, Yuen was the first to report in the Lancet about the unusual clinical severity and high mortality of infected patients, which could be identified by the in-house molecular test at his laboratory. Yuen became the Scientific co-director between the HKU-Pasteur Research Centre and the University of Hong Kong in 2000.Overseeing the research of microbes which are used by the Hong Kong government to control and contain epidemics. During the global outbreak of severe acute respiratory syndrome (SARS) in 2003, he led his team in the discovery of SARS-CoV-1, and subsequently traced its genetic origins to wild bats. For these achievements he was honoured by Time Asia magazine as one of its "Asian heroes of the year" in 2003. He has led his team in the discovery of other disease agents, such as the novel Human coronavirus HKU1, bat coronavirus HKU2 to HKU13, Laribacter hongkongensis and many other bacteria named after Hong Kong or China. Yuen is currently the Chair of Infectious Disease at the Department of Microbiology of the University of Hong Kong. He co-directs the State Key Laboratory of Emerging Infectious Disease of China in Hong Kong. He is also a member of the Chinese Academy of Engineering (Medicine and Health section). COVID-19 pandemic Yuen is involved in the research on SARS-CoV-2, the virus responsible for the COVID-19 pandemic. He was an early advocate of wearing masks even by healthy individuals, citing asymptomatic cases and a large number of virus strands in saliva of an infected person.