1. When the prostitutes in townget so overloaded with STDs that it becomes visible via fungus growth, and you are forced to migrate to another part of the city to find ones with a health rating of at least 23%.
2. When a straight person turns gay, or vice versa.
1. I'm gonna start plowing new ground around 4th street tonight man. Last night one of the regulars on 3rd blew up a car with her yeast infection.
2. Fred's hanging around the women's section in Kmart for a different reason since he's turned straight. He's plowing new ground now.