I was hoping for a little more out of this movie. It is set in a hospital, which is an inherently creepy setting that has been used to good effect in several good horror movies (eg, Session 9, the Eye 2). Unfortunately, though the cinematography is good, there's not much in this movie that rises above the sort of low-level creepiness inherent in all hospitals.
At times I was struck with the idea that the director had originally planned to make a fairly straight-forward hospital-slasher movie, but due to some kind of colossal blunder ended up being shipped 50 gallons of green goo instead of the 50 gallons of fake blood that he ordered. Infection was then swiftly rewritten to accommodate this mix-up, and while they were at it they tacked on some twists at the end which might have been fresh prior to the global movie-twist mania that swept the world circa 1993 or so.
It's not a terrible movie, and there is some endearing acting by the three lead doctors (who do fairly well with pretty colorless characters). Overall, though, it plays out like a Halloween episode of E.R. Many scenes that ought to frighten the viewer are just drawn out, only the most extreme of the gross-out scenes are really effective, and the movie is full of dross that doesn't enhance its story or its mood.