Orf (a zoonotic disease)

Sounds nasty, looks nasty too. Orf is a disease of sheep that's transmitted to humans and can affect farm workers, shearers, butchers and abbattoir workers. Starting as a dark-red spot on your face, hand or arm, it enlarges to to 1-4 centimetres in size, grows a head, and fills with a clear fluid which turns into pus. You're likely to feel sick as well (hardly surprising). The good news that orf does clear up completely within three weeks.