Why do so many people in Africa have AIDS if it is an STD?

AIDS is not primarily spread through sexual contact in sub-Saharan Africa. According to UNAIDS, heterosexual sex accounts for less than 50% of new HIV infections in the region. The primary mode of transmission in Africa is through mother-to-child transmission and through unsafe injections such as contaminated medical needles as stated by WHO. Furthermore, in many African countries stigma, discrimination, gender inequality, weak health systems and poverty hinder effective AIDS prevention efforts.