Donald Sutherland took over from Joe Don Baker because director Petersen and producer Kopelson wanted the character to have more of an "Oliver North quality" and decided Sutherland could deliver that. Sutherland was not available for filming when production began, but later joined the set and was able to complete all of his scenes without any delays.
The music and (briefly seen, somewhat blurred) footage of a cartoon seen in the movie theater scene is from the Tom & Jerry episode Polka-Dot Puss (1949). It's appearance in Outbreak is somewhat apt, as in the cartoon, Jerry tricks Tom in to believing he has caught measles, and then proceeds to 'cure' him. The episode ends with both Tom and Jerry actually contracting measles and being quarantined.
Betsy, the white-headed capuchin Monkey, also appears in the sitcom Friends (1994) as Marcel, Ross' pet. The monkey's prior role in Outbreak was spoofed by a poster showing Marcel as the star in the fictional movie "Outbreak 2: The Virus Takes Manhattan". Both the movie and the TV series are Warner Brothers productions.
When investigating the village in Zaire several of the huts are burned down. This is the traditional tribal method for controlling the spread of an infection in many parts of the world. Food and water are left outside the entrance to the dwelling and the occupants cannot leave. If several days (usually 3 or 4) of these supplies are not used then the dwelling is burned down to stop the infection from spreading.
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.
The trivia item below may give away important plot points.
The bomb that explodes in the ocean was scripted to explode over the town, vaporizing it. Boss Film actually did the effects sequence showing the destruction, but test screenings forced the filmmakers to re-shoot the end with the town being saved.