1 Unité de Recherche sur les Enjeux et Pratiques Humanitaires (UREPH), Médecins Sans Frontières (MSF), 78 rue de Lausanne, 1211 Geneva, Switzerland. Electronic address: philippe.calain@geneva.msf.org.
2 Department of Microbiology and Molecular Medicine, University of Geneva School of Medicine, CMU, 9 Avenue de Champel, 1211 Geneva, Switzerland.