We're creating these massive urban areas in the Third World. It's like you take the entire population of California and put it in one city. Then you remove basic sanitation and medical services, and you have a ticking biological time bomb.

If a vaccine works, then the vaccinators might conceivably set up what's known as ring vaccinations around Ebola hot spots. In this technique, medical workers simply vaccinate everybody in a ring, miles deep, around a focus of a virus.

If a vaccine works, then the vaccinators might conceivably set up what's known as ring vaccinations around Ebola hot spots. In this technique, medical workers simply vaccinate everybody in a ring, miles deep, around a focus of a virus.