 A week into filming, Francis felt the infected (referred to as "Darkseekers" or "hemocytes" in the script), who were being portrayed by actors wearing prosthetics, were not convincing.His decision to use CGI resulted in an increased budget and extended post-production, although the end results were not always well received.The concept behind the infected was that their adrenal glands were open all of the time and Lawrence explained, "They needed to have an abandon in their performance that you just can't get out of people in the middle of the night when they're barefoot.