I study HIV/AIDS and the stigmas surrounding it
I think the big obstacles that the world faces with regards to HIV/AIDS and stigmas are shame, and the desire to perpetuate the power structure created by HIV/AIDS. Both of those seem to prevent education from being seen as a viable option in places like South Africa.

On a more personal note, as a member of the LGBTQ community, I have seen a lot of public shaming associated with anyone who contracts an STI. This results in people not talking about their STIs, and then we have more STIs...