The Apes of Wrath Garth Marenghi's Darkplace : Season 1 Episode 4

A mysterious illness spreads like a particularly virulent disease through the wards of Darkplace, causing doctors and patients to revert to a primal state. It's up to Dr Rick Dagless, M.D. to stop it before he too turns into a chimpanzee or an orang-utan or something like that.