To promote this film, Warner Bros. Pictures Canada built two giant Petri dishes treated with bacteria and fungi and set them in a Toronto storefront window. Over several days, the bacteria and fungi specimens grew to spell out the name of the film and form biohazard symbols.
Consultant Dr. Ian Lipkin - professor of epidemiology at Columbia University's Mailman School of Public Health - said the virus in the film is one he created based on some traits of the Nipah virus from Malaysia in the late 1990s which spread from pigs to farmers.
In the magazine New Scientist's article "Contagion doesn't skimp on science"(15/9/2011), the author writes that: "It's hard to name many Hollywood blockbusters that are as invested in the realities of science as Contagion", "Although it is by no means flawlessly accurate - it's not a NOVA documentary - Contagion has been well fact-checked compared to most science/y blockbusters", "...very few Hollywood productions realistically portray the process of science, both its successes and frustrations. That's what makes Contagion unique".
Steven Soderbergh and Scott Z. Burns were planning to follow up The Informant! (2009) with a biopic about controversial German director Leni Riefenstahl, but Soderbergh decided to abandon that project because it would have a very limited potential audience. The two men then came up with an idea for a suspense and drama look at a worldwide medical crisis, which they fine-tuned into this film.
The key to growing the virus was "a fetal bat cell line from Geelong". This refers to the Australian Animal Health Laboratory, a high security laboratory for exotic animal diseases in Geelong, Victoria, Australia.
The actual desk of Benny Evangelista, reporter for the San Francisco Chronicle, appears in the film as Lorraine Vasquez's desk. Evangelista's desk is notoriously messy, and was left as it was by the crew.
The Russian title of the film ("Zarazhenie") contains nine letters, like the English one, and the poster of the film also mentions nine cities' names with one letter highlighted and the highlighted letters form the name of the film. They are, from top to bottom: kaZan, atlAnta, san fRancisco, chicAgo, pariZH (Paris), gEneva, loNdon, tokIo (Tokyo), pErm - Z-A-R-A-ZH-E-N-I-E. Kazan and Perm are Russian cities.
A number of the actors in this film have also appeared in superhero films: Gwyneth Paltrow (Iron Man series, Avengers series), Laurence Fishburn (Superman series), and Monique Gabriela Curnen and Chin Han (Batman Series). Jennifer Ehle also has a superhero connection in that her mother, Rosemary Harris, was in the Spiderman film series.
The trivia item below may give away important plot points.
A scene where Dr. Ally Hextall (Jennifer Ehle) injects herself with the vaccine was re-shot at the suggestion of consultant Dr. Ian Lipkin, because her scientist character was inappropriately shown injecting the needle through clothing.