I like the idea of subtle, flu like symptoms as well. Promotes paranoia, adds drama. Since this is a work of fiction, I don't know that pulling up projections on demographics is entirely necessary, although it would be interesting just to see that data, admittedly. I think it is fair to assume that there will be a higher incidence of unemployment, a larger working class, and higher ethnic minority populations, as well as considerably more people of mixed ethnic heritage. May sound cliche or racist or whatever, but I think it is safe to assume that in such a society, regardless of whites moving towards being a minority, they would likely still have more wealth on average, or at least those making up the highest income brackets would still be overwhelmingly white. Not sure I know what you mean as far as alternate timeline for medicine and technology. Do you mean advancements, hindrances in progression that make such a plague scenario more likely?