1 Centre for Tropical Medicine and Global Health, Nuffield Department of Medicine, University of Oxford, UK and KEMRI-Wellcome Trust, Kilifi 80108, Kenya.
2 Institute of Tropical Medicine and International Health, Charité University Medicine, Berlin 10117, Germany.
3 Human Health Theme, International Centre of Insect Physiology and Ecology, Nairobi 00100, Kenya.
4 Institute of Microbiology and Infectious Diseases Immunology, Charité University Medicine, Berlin, Germany.