1. Swiss Tropical and Public Health Institute, Kreuzstr 2, CH-4123, Allschwil, Switzerland
2. Faculty of Medicine, University of Basel, Petersplatz 1, CH-4001, Basel, Switzerland
3. Faculty of Science, University of Basel, Petersplatz 1, CH-4001, Basel, Switzerland
4. Institute of Community and Public Health, Birzeit University, Birzeit, P.O. Box 14, West Bank, Palestine