The image is at face value a plus-or-minus sign. In this design it is meant to be a sign to everyone that, whether you are someone who has AIDS, you are a friend/loved one affected by it, or even if you don't directly know someone who has it, you can still retain a positive outlook on the situation. It is an all-inclusive symbol, calling for us all to stay informed, aware, and compassionate.
I have a few iterations of the design. I am liking the second version (hand-drawn) the most, I think.