This is an original script containing Ted Tally's (Silence of the Lambs, Red Dragon) revisions to the original screenplay by Laurence Dworet and Robert Roy Pool dated May 13th 1994.
This film won a development battle with a similar viral-outbreak thriller project at 20th Century Fox called "Hot Zone". That film was going to be directed by Ridley Scott and star Robert Redford and Jodie Foster, but ran into script problems that threw it off stride. When producer Arnold Kopelson hired Ted Tally to work on his script, he liked the results so much that he immediately sent it out to Harrison Ford; Ford declined, but then Dustin Hoffman and Wolfgang Petersen signed on to star and direct, and Warner Bros. greenlit the film for a 1995 release.