 In their virus discovery research, Wuhan researchers searched for new bat viruses in caves in southern China, brought samples to Wuhan, and sequenced, cultured, and characterized new viruses in Wuhan. In their gain-of-function research, Wuhan researchers genetically modified bat SARS viruses, constructing viruses having enhanced ability to infect human cells and having enhanced viral growth and enhanced lethality in mice engineered to possess human receptors for SARS viruses, so-called humanized mice.