1. Division of
Biology, MC 156-29, California Institute of Technology, Pasadena, California
91125, United States
2. Institute of Molecular and Genomic
Medicine, National Heath Research Institutes, 35 Kayen Road Zhunan Mioali, Taiwan
3. MRC Center for Outbreak Analysis & Modeling, Department of Infectious Disease Epidemiology, Imperial College London, London W2 1PG, U.K.