Thrax is the main antagonist of the movie Osmosis Jones and is a deadly virus that comes from a filthy egg. According to some fan theories, Thrax is the rabies virus because he attacks the brain. Other theories suggest that Thrax is a cytomegalovirus that has become lethal or a human immunodeficiency virus. While Thrax is short for anthrax, which is a bacterial disease, the microbe is referred to as a virus in the movie. However, it is not clear what kind of virus Thrax is supposed to be, and the movie leaves it open to interpretation.