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 s

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.