It starts as slow burn until it hits a relatively moderate pace of action. The buildup isn't necessarily boring if you don't mind a slower introduction. My only gripe is the lack of exploration into the more interesting aspects that would have led the movie into a more entertaining spectrum. I enjoy movies with unleashed viruses/organisms, however, this movie glossed over what could have been an excellent addition. That being said the movie has it's share of twists and leads you into an unsuspected ending. I give it points on its amusing venture within that aspect. Overall an entertaining film for those who appreciate suspenseful horror and have seen just about everything and are teetering on the edge of viewing this one.