Now if virus can infect lesser/greater form of specie, it can infect its counterpart.
Also made viruses affect only joinable species to lessen a chance of spawning a virus that they can't work on (e.g. slime-affecting viruses that can't be injected into monkeys). As a side-effect viro reports are a little less inane listing all the species crewmembers aren't supposed to know about like xenomorphs and Shadows.