Coronavirus outbreak raises question: Why are bat viruses so deadly?

A study of cultured bat cells shows that their strong immune responses, constantly primed to respond to viruses, can drive viruses to greater virulence. Modelling bat immune systems on a computer, the researchers showed that when bat cells quickly release interferon upon infection, other cells quickly wall themselves off. This drives viruses to faster reproduction. The increased virulence and infectivity wreak havoc when these viruses infect animals with tamer immune systems, like humans.