1. School of Medicine, University of California, Mission Hall, 550 16th St, San Francisco, CA 94158 USA
2. Department of Global Health and Population, Harvard T.H. Chan School of Public Health, 677 Huntington Ave, Boston, MA 02115, USA
3. Travel Medicine Center, Mount Auburn Hospital, 330 Mt Auburn St, Cambridge, MA 02138, USA
4. Harvard Medical School, Boston, 25 Shattuck St, Boston, MA 02115, USA