1 aCentre for Geographic Medicine Research - Coast, Kenya Medical Research Institute (KEMRI), Kilifi, Kenya bNuffield Department of Medicine, University of Oxford, Headington, UK cDepartment of Global Health, Academic Medical Centre, University of Amsterdam, Amsterdam, the Netherlands dCenters for Diseases Control and Prevention, Atlanta, Georgia, USA eNational AIDS and STI Control Programme (NASCOP) fMinistry of Health, Nairobi, Kenya gDepartments of Medicine, Global Health, and Epidemiology, University of Washington, Seattle, Washington, USA.