Resident Evil's many viruses and infections are "an important and terrifying staple of the series," according to a recent Resident Evil: Revelations developer diary.
Director Kazuhisa Inoue explains in the video above that the series uses viruses as a recurring theme because of their commonality.
"We can't see viruses but they permeate the air around us," Inoue said. "They're everyday yet scary at the same time. From that starting point, we created Zombie-like creatures, as well as the ‘Ooze,' which are frightening because they originate from something we see in action in our everyday lives."
Interface designer Akiko Hashimoto also explains the game's mutating characters. Hashimoto said that these characters inspire fear because they remind players what will happen if a loose virus isn't contained.
Resident Evil: Revelations will launch for Windows PC, PlayStation 3, Xbox 360 and Wii U May 21.