With nuclear weapons, you'd think you would probably stop after killing 100million. Smallpox won't stop. Because the population is naïve, and there are no real preparations. That, if it got out and spread, would be a larger number.

We all have the chance to create a world where extreme poverty is the exception rather than the rule.

To be a good professional engineer, always start to study late for exams because it teaches you how to manage time and tackle emergencies.

Anyway, the US, as in most issues, is the best, has the best capability to lead, and really needs to lead. It doesn't [mean] that other countries won't pick different tacks and emphasize different things. In aggregate, they're almost half of the energy R&D. Europe, China, Japan - it's very important that they come along and contribute to these things.

Going out in the field, it's always enlightening to see what's working and what's not and to sit down and talk - I was with young girls in south Africa - understanding why our tools for prevention aren't being adopted, and what way may need to invent to help protect them.

The fight against AIDS in China is already well underway. The Chinese government and other funders are providing major support, and they'll continue to bear primary responsibility for delivering prevention and treatment.

[Africa] is the one continent where you still have a lot more young people than old people. So making sure they're healthy, good nutrition, good education. That'll be important for the world.