(Not OP) Viral infection can have this effect. The flu for sure, but also the varicella virus (i think this is the translation?) do too. West Nile virus also?

(Not OP) Viral infection can have this effect. The flu for sure, but also the varicella virus (i think this is the translation?) do too. West Nile virus also? Its definitly not the majority of viruses, and i'm not sure bacterial (benefit of the doubt here). Don't tell me you never exagerate a little :P