When Christopher Murray was 10 years old, he and his family packed a few suitcases and a portable generator and left their home in Golden Valley, Minn., for a flight to England. From there they traveled by car and ferry to Spain, to Morocco and finally through the Sahara Desert to the village of Diffa in rural Niger. For the next year the family of five, led by a physician father and microbiologist mother, set up and then administered the local hospital. As the young Murray tended the hospital pharmacy and ran errands, he could not help noticing that the citizens of Niger came down with all kinds of odd diseases that nobody had back in Minnesota. He recalls wondering, “Why are people in some places so much sicker than in other places?”