There are several hundred people who stayed in the Ebola-affected countries and continued to do the work, put themselves at great risk because medical workers are the most likely to be infected because they're helping out when the person's health is deteriorating, including quite a bit of bleeding as they're getting very, very sick.

Cutting through complexity to find a solution runs through four predictable stages: determine a goal, find the highest-leverage approach, discover the ideal technology for that approach, and in the meantime, make the smartest application of the technology that you already have - whether it's something sophisticated, like a drug, or something simpler, like a bednet.

When a country has the skill and self-confidence to take action against its biggest problems, it makes outsiders eager to be a part of it.

I would certainly use my voice to try and avoid anything that undermines confidence, so that parents are using vaccines fully.

We really have to work hard to remind people even though this is far away, that's it's probably the most generous thing governments have ever come together to do. Since World War II, this new institution is the only one that's emerged and is saving all these lives.

As we have taken diarrhea and pneumonia down, even malaria down quite a bit, the portion of the days that are very early in that 5 years - the first month, the first day - it's about half now. Yet that's the part we understand the least.

Software is inherently complicated. If you say to somebody I want an airline reservation system, to really say what you want in terms of overbooking and fares, and different airlines communicating with each or schedule changes, it's immensely complex. And so you can't write a program that's any simpler than that full specification.