In 28 Days Later the Rage Virus causes uncontrollable aggression and changes in personality. Is such virus even possible in principle? I'm not talking about rabies but rather about a genetically engineered virus that causes those symptoms. Maybe by inserting genes responsible for adrenaline or vasopressin release. Of course I know the time shown in the movie to change a person (a couple seconds) is impossible.
No, but maybe yes.
The idea of parasites or other diseases that can cause changes to behaviour is well established. For example there is fungus that takes control of ants. There are parasites that make mice and rats get eaten by cats. Rabies is a classic example as well.
But changes as drastic as those shown in 28 days later? That's a bit more of a stretch.
A virus (or any other disease) that spreads as fast and acts as fast as that in 28 days later? That doesn't seem reasonable. It just can't infect and multiply in a host that quickly.
So a weaker, slower spreading version? Maybe. As shown in the films? No.