1. Biomedical and Environmental Thematic Group, Ifakara Health Institute, PO Box 53, Ifakara, Tanzania
2. Department of Mathematics, Statistics, and Computer Science, Marquette University, Milwaukee, WI 53201-1881, USA
3. Department of Epidemiology and Public Health, Swiss Tropical and Public Health Institute, Basel, Switzerland
4. University of Basel, Basel, Switzerland
5. Liverpool School of Tropical Medicine, Vector Group, Pembroke Place, Liverpool L3 5QA, UK
6. Department of Infectious and Tropical Diseases, London School of Hygiene and Tropical Medicine, Keppel Street, London, WCIE 7HT, UK