mmm...know a lot of schools have 4th year electives that you can do abroad. Think georgetown might have some program, but I know Baylor has a pretty reputable international health track (http://www.bcm.edu/medschool/tracks/international/index.htm)
You're probably not interested in this but there's a school in Israel called Ben Gurion University the entire focus of which is International Health. It's affiliated with Columbia.
University of Michigan, Harvard, and Ohio State have strong history of global health initiatives. I my friends (3rd and 4th year students) at Ohio State that even started "the ride for world health" http://www.amsa.org/r4wh/rider.cfm
Indiana University has a study abroad elective in Kenya. I believe you can do it your 2nd yr during the summer. You go with a bunch of students along with a faculty member.