List the basic modes of transmission of HIV. Have they changed substantially over the last 20 years?

The basic modes of transmission of HIV include unprotected sexual contact, sharing of needles or syringes, transmission from mother to child during pregnancy, birth or breastfeeding, and exposure to infected blood or blood products. These modes of transmission have not substantially changed over the last 20 years, although there has been an increase in access to antiretroviral therapy and efforts to promote safer sex practices and harm reduction strategies such as needle exchange programs. However, stigma and discrimination continue to be barriers to prevention and treatment efforts.