Yuen's information videos on preventing the spread of the virus are published on the website of the University of Hong Kong. Yuen caused controversy when he and co-author David Lung published an op-ed article titled "The pandemic originated from Wuhan and the lessons from 17 years ago have been forgotten." in the Chinese-language newspaper Ming Pao, stating that the trading and consumption of wild animals was a result of the inferior culture of Chinese people. The authors later retracted the article and apologised for the statement. In an interview with the BBC, Yuen accused the Chinese authorities of covering up the scale of the virus. He claimed that he alerted mainland health officials on 12 January 2020 to suspected human-to-human transmission of SARS-CoV-2. This warning was not made public until 19 January. He also accused the authorities of destroying evidence: "When we went to the Huanan supermarket, of course, there was nothing to see because the market was clean already. So, you may say that the crime scene is already disturbed. Because the seafood market was cleared, we cannot identify the animal host, which has given the virus to humans.", said Yuen. Yuen was one of the lead authors of an article in Clinical Infections Diseases, published in August 2020, which described the first proven case of a COVID-19 reinfection of a patient with a different strain of SARS-CoV-2. Timeline On 6 December 2020, during the fourth wave of the COVID-19 pandemic in Hong Kong, Yuen said that the wave had been expected and urged the public to remain vigilant with regard to social contacts on Christmas. At the same time, he expressed his confidence that the wave would remain under control if the city went back to the social distancing measures that had been in place in July. In an opinion article published by Kwong together with fellow microbiologists Lung and Kelvin Chiu in Ming Pao on 25 August 2021, the authors argued that it would be impossible to eradicate COVID-19 due to the constant appearance of new strains, as well as the presence of asymptomatic cases, which distinguished it from smallpox, the only disease which had been successfully eradicated. They urged Hongkongers to get vaccinated as soon as possible. On 22 November 2021, a public health investigation concluded with the finding that one of two cases of the Omicron variant at a quarantine hotel had likely been infected