Annelies Wilder-Smith1, Priscilla Rupali2. 1. Department of Disease Control, London School of Hygiene & Tropical Medicine, London WC1E 7HT, UK; Heidelberg Institute of Global Health, University of Heidelberg, Heidelberg, Germany. Electronic address: annelies.wilder-smith@lshtm.ac.uk. 2. Christian Medical College, Vellore, Tamil Nadu, India.