1. a Department of Environmental Sciences and Engineering, University of North Carolina at Chapel Hill Gillings School of Global Public Health, 135 Dauer Dr., Chapel Hill, NC 27599, USA
2. b School of Medicine, Uniformed Services University of the Health Sciences, 4301 Jones Bridge Rd., Bethesda, MD 20814, USA
3. c School of Medicine, Stanford University, 291 Campus Dr., Stanford, CA 94305, USA
4. d U.S. Naval Medical Research Unit-Two, Singapore, Singapore