For almost a decade, scientists chased the source of a deadly new virus through China's tallest mountains and most isolated caverns. They finally found it in the bats of Shitou Cave. The virus in question was a coronavirus that caused an epidemic of severe acute respiratory syndrome, or SARS, in 2003. So what exactly is a coronavirus, and how does it spread? Elizabeth Cox explains. [Directed by Anton Bogaty, narrated by Bethany Cutmore-Scott, music by Jarrett Farkas].