(at around 1h 5 mins) When Cal and Dr. Fairchild free fall through the air intake in the greenhouse, after they crash through the ventilation panels, Cal's suit rips wide open by the groin area. This rip is a significant rip that would expose him to the infection. Yet, it is never addressed in the movie.
(at around 14 mins) When the P4 lab identifies the infection with the violent animals, a gun is shown putting them down. It then cuts to what is obviously Dr. Fairchild throwing the corpses into the incinerator. He would not be introduced until later in the film. It is likely the scene was edited from later in the movie when he and the Sheriff enter the facility.
(at around 1h 30 mins) As the antennas automatically fold up on the roof of the command center, a hand can be seen reaching up and catching one.