1. Department of Mathematics, University of Florida, Gainesville, FL, USA
2. Department of Epidemiology and Biostatistics, College of Public Health, University of Georgia, Athens, GA, USA
3. Center for Ecology of Infectious Diseases, University of Georgia, Athens, GA, USA
4. Department of Mathematics, Tulane University, New Orleans, LA, USA
5. Emerging Pathogens Institute, University of Florida, Gainesville, FL, USA
6. Department of Biology, University of Florida, Gainesville, FL, USA
7. South African Centre for Epidemiological Modelling and Analysis, Stellenbosch University, Stellenbosch, South Africa
8. Department of Mathematics, Tulane University, 6823 St Charles Avenue, New Orleans, LA 70118, USA