The Virulence Protocol by D.G. Chichester

As Captain of the interstellar CSS Jonas Salk, your mission has always been clear and corporate: pirate the living specimens of alien worlds, seeking new biologies that can be exploited for medicine and profit. Something about that must not have sat right with the universe. Because what your crew found last expedition is not a cure, but a curse. A virus now eats away at all of you, raising tensions and terror inside the ever more claustrophobic spacecraft. With no established protocol for this level of infection, it's up to you to decide whether to contain the virus — or let the malice find its way back to Earth.