Last year my wife, Melinda, and I visited an AIDS clinic in Durban, South Africa. We met women who had walked miles from nearby townships. When they arrived, they were greeted by a well-trained staff. There was an ample supply of antiretroviral drugs, which can help people with AIDS stay healthy for years. Patients were receiving counseling. As we chatted with one of the doctors in the clinic, it struck me: something was fundamentally different.