Confusion at the hospital

Mrs. Smith had just gotten home from visiting her husband in the hospital. He had fallen ill and the doctors weren't sure what was wrong with him so they wanted to keep him at the hospital for observation. Mrs. Smith had just walked in the front door and was setting her purse down when the phone rang.

"Hello?" said Mrs. Smith.

"Yes, Mrs. Smith, this is Mary calling from the hospital. I'm afraid I've got some bad news and some worse news about your husband."

"Oh dear," said Mrs. Smith, "I guess I'll take the bad news first."

"Well," said the nurse, "The bad news is that we got the test results back for your husband but there's been a bit of a mix-up. It seems that there's another patient at the hospital with the same name as your husband, Bob, and we're not sure which test result belong to which patient. One of the tests came back positive for Alzheimer's disease and the other test came back positive for AIDS."

"Oh my goodness," said Mrs. Smith, "Well that's horrible. What news could be worse than that?"

"The worse news is that we can't find your husband. He left his room and we're not sure where he went," said the nurse.

"Oh my god!" exclaimed Mrs. Smith, "What do you suggest we do?"

"Well," replied the nurse, "if your husband finds his way home, don't have sex with him."