Reasons 1, 2, and 3 are health. The African-American community has more serious health problems, on average, than other races in the US. I'm not smart enough to know how much culture and socioeconomic status influence this.

The other reasons tie largely to poverty. 4 and 5 are about being susceptible to it spreading, and 6 and 7 are about quality of healthcare.

4. On average, the impoverished communities in cities are more densely packed than the suburbs and richer areas of town.

5. Poorer people generally have less opportunity to work from home, so they are on buses and at work interacting with far more people than the average person.

6. Poorer people generally have poorer healthcare, in both quality and in out-of-pocket costs. This disincentives hospital trips in general.

7. Hospitals and medical facilities nearby aren't as nice as those in the suburbs or richer areas of town.

Edit: Organization