1. Department of Environmental Health and Engineering, Johns Hopkins Bloomberg School of Public Health, Baltimore, Maryland, USA
2. Department of Pathology, Johns Hopkins University School of Medicine, Baltimore, Maryland, USA
3. Rural Empowerment Association for Community Help, Warsaw, North Carolina, USA
4. Department of Epidemiology, Johns Hopkins Bloomberg School of Public Health, Baltimore, Maryland, USA
5. Department of International Health, Johns Hopkins Bloomberg School of Public Health, Baltimore, Maryland, USA