Is it possible that a virus can cause mental illness?

This sounds an awful lot like glandular fever. The first thing to do is to stop blaming yourself. You are unwell, there's nothing you can do about that at the moment. But it isn't your fault, you've just been unlucky. As to whether or not a virus can cause mental illness; the answer is sort of, sometimes. I suffered something called toxic confusional delirium after having a virus that landed me in ITU. Basically I was psycotic for six months. I kept trying to jump out of windows because the people that I was hallucinating frightened me to death. it will p, remember that. Just keep reminding yourself of what is real and what isn't, and eventually your brain will start to behave. A lot of viruses can cause depression, so watch out for that. it does p eventually, but you really need to look after yourself. So eat right, sleep properly etc, and you'll get there in the end. I wish you all the best and I genuinely hope this misery ends for you soon.