Noomi Rapace had her nose fractured when she was elbowed accidentally while filming a fight scene. She didn't realize the extent of the injury until much later so, after a brief black out, she insisted on carrying on with the scene. As of April 2015, the fracture had yet to be mended and had healed crocked.

Although primarily set in London, the budget didn't extend to shooting the entire film there. Instead, most of it was shot in Prague with six days' location work in London.

One of the big action setpieces was originally supposed to be in Paris but had to be quickly relocated after terrorist attacks in the city.

The biological weapon mentioned is the Marburg virus, which is a hemorrhagic fever virus and has symptoms resembling ebola. There is no known cure, but consumption of a great deal of fluids at the onset can aid in survival. The virus is spread by human contact, as well as some species of bats. It is so serious that when two tourists contracted it when visiting the Kitum cave at Mount Elgon in Kenya, the United States Army Medical Research Institute of Infectious Disease (USAMRIID) sent a team in an attempt to identify the two different vector strain presumably residing in the cave (no traces were found). These events formed the basis of the best-selling book The Hot Zone by Richard Preston.

The screenplay for this film was featured in the 2008 Blacklist; a list of the "most liked" unmade scripts of the year.