Andromeda Strain

A deadly, green, crystalline, extraterrestrial agent of indeterminate origin. It erodes the vessel walls of the circulatory system, causing death by either triggering the body's coagulation response (resulting in the entire system clotting in a few seconds), or by cerebral hematomas (accompanied by dementia) if clotting is prevented. It evolves at a rapid rate, is spread by airborne transmission, and is extremely contagious. Its in the book by Micheal Crichton and the two movies.