How does the spread of AIDS among African Americans confirm that health is a social, rather than simply a medical problem?
The spread of AIDS among African Americans shows this because social factors are behind much of the spread.
For example, the cdc.gov link below tells us that 73% of the new cases of AIDS among African American men are contracted through men having sex with men. In the African American community, homosexuality tends to be more stigmatized than it is in the white community. Therefore, African American men will tend to shy away from things like getting HIV tests because they are afraid that their sexuality will be discovered. The CDC also believes that lack of exposure to HIV and AIDS education among poorer people is another cause of the spread of AIDS among African Americans.
In both cases, these are social factors, not medical factors, which are helping to spread AIDS. This illustrates the way in which health is social as much as it is medical.