Why? What’s their motive? The walking dead wants everyone to share fair in their walking death, and subsequently their very real death.
As outrageous as that sounds, that is exactly their motive. They want AIDS to be "everyone's problem" as they frequently advertise, so that more research funding for a cure will be supplied by taxpayers, and so that they can salve what consciences they have left with the idea that normal people are also infected. Anything to avoid culpability.