A joke told by my mother's cousin

A woman has been feeling ill for weeks, so her husband takes her to the doctor. They run some tests on her, and, a few days later, they call with news of the results. The husband answers the phone.
"Well, doctor," he says. "What's wrong with her?"
"Unfortunately," the doctor says, "we had a chart mix-up with another patient, and we don't know which one is your wife's. At any rate, the news isn't good. She's either got AIDS or Alzheimer's."
"Oh my god," the man says. "What should I do?"
"Well," the doctor says. "Drive her three miles into the country and drop her off. If she finds her way back home, don't fuck her."

Ba-dum bum ching!