The biggest public health challenge is rebuilding health systems. In other words, if you look at cholera or maternal mortality or tuberculosis in Haiti, they're major problems in Haiti, but the biggest problem is rebuilding systems.
But, I would say when I was four years old and I was at the Alan King Tennis Tournament and I was hitting with all the pros that would come to town. They would get me on the court or take notice and that stayed with me.
Childhood didn't have a big influence on me, really - in fact I spent most of it plotting how to escape.