Chao says that most of the more than 500 viruses in the baculovirus family have a specific host species, which means they cannot infect other species.
趙裕展指出，桿狀病毒有五百多種，大部分各有宿主，不會交互感染，例如家蠶桿狀病毒便具有「專一性」，只會感染家蠶，不會感染其他昆蟲。