In low-income countries, the main problems you have is infectious diseases.

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.

Whether it's Google or Apple or free software, we've got some fantastic competitors and it keeps us on our toes.

China is certainly an important player in the global economy, and a widespread AIDS epidemic would threaten that growth.

The AIDS is a disease that is hard to talk about.

The human body is the most complex system ever created. The more we learn about it, the more appreciation we have about what a rich system it is.

When I was trying to figure out why lives have improved so much in the last 300 years, where we've gone from a third of kids dying before 5 to - by 1990 it was down to 10% - now it's down to 5%. And saying why, over all history, there were smart people, but that number didn't change. Average life span didn't change. What's magical about what's been deemed the Industrial Revolution? It's really energy intensity.