Education is a critical one. Lack of stable relationships in poor communities (money issues being a key factor in many divorces). Injection drug use without sterile supplies (which cost money in most places). Substance abuse is higher in some poor communities in the US, which even aside from injection drugs might be an accelerant for HIV transmission, e.g. drunk people may not practice safe sex even though they normally would, or they may have sex with people they normally would avoid.

HIV is just waiting to get you because of your low bank balance.

Well played. I laughed, but see my reply to another commentor: https://news.ycombinator.com/item?id=6949440

I admit without my more detailed explanation, you'd be right. low bank balance is just as absurd a cause for increased HIV infections as my brown skin is.

Your explanation of why socio-econimic status might be correlated with HIV makes sense.

However I still think your dismissal of race as having independent explanatory power is wrong.

For example, race has independent explanatory power in predicting crime rates, even after taking into account many other social and economic variable. This doesn't mean that skin color causes crime, e.g. there could be (and almost certainly are) very many social factors that are correlated with race but hard to measure objectively.

Ah, well if you're poor & living in a poor neighborhood then the following are more likely:

  - Low income tends to imply low education, so maybe not
   fully understanding the risks of HIV. 
  In some parts of Africa they think(thought) 
  that sleeping with a virgin would cure men of HIV. 
  That's an education problem in the poorer parts of the continent.

  - Prostitution is probably nearby.

  - Stress of life living paycheck-to-paycheck, can't 
  afford vacations, one of the few things you can enjoy 
  at some random parties & nightclubs is random hook-ups
  with whatever person you can get.

  - Drugs an unclean needles 'n such.

With well off people those above still happens, but in a different way sorta.

- middle-class to wealthy understand how HIV works for the most part and will more often avoid the risky behaviors

- Prostitution is not needed when you can hook-up with the random co-worker or at some university party with smart people who are more likely than not HIV-free. Then there's what I like to call "high class legal prostitution": http://www.prlog.org/12074839-gold-digger-cruise-connects-be... We know what's probably happening on that cruise... Also expensive high class gentlemen's clubs...

Drugs for middle-class/rich? They don't have to buy/share them off the street from random people like poor people have to. They order from reddit's sheepmarketplace or silkroad!!!