1. Program in Population Biology, Ecology and Evolution, Emory University, Atlanta, Georgia, USA
2. Department of Epidemiology, University of Michigan, Ann Arbor, Michigan, USA
3. Department of Epidemiology & Biostatistics, Michigan State University, East Lansing, Michigan, USA
4. Department of Microbiology and Molecular Genetics, Michigan State University, East Lansing, Michigan, USA
5. Instituto de Microbiología, Universidad San Francisco de Quito, Quito, Ecuador
6. Universidad Central del Ecuador, Quito, Ecuador
7. Department of Anthropology, Trinity College, Hartford, Connecticut, USA
8. Department of Environmental Health, Emory University, Atlanta, Georgia, USA