Dear Doctor Bob, My dog licked a used condom in the park then when we got home (unbeknown to me) he drank tea out of a cup. Then my brother drank out of the same cup and my sister got the dog's saliva on her fingers and ate a sandwich. Could my brother and sister get infected with HIV?

Hi,

This sounds like one of those absurd math equations everyone hated in high school: Train A leaves the station at 10 AM heading west to Station B at 50 miles per hour while Train B leaves Station B at the exact same time heading east at 35 miles per hour and a little puppy named Toto is asleep on the tracks two thirds of the way from Station A to Station B. Which train squishes Toto to smithereens first? (The answer is neither because Toto would wake up and get off the tracks when he heard the trains coming.)

As for your dog licking used condoms, drinking tea out of a cup and your brother using the same cup and your sister getting dog spittle on her fingers before she munched on her PB&J sandwich (with the crust cut off), there is absolutely no HIV-transmission risk. None. Zero. Zip. Nada. If HIV were transmitted that easily, it would have wiped out the planet long ago.

Dr. Bob