[1] Univ Calif Los Angeles, Dept Epidemiol, Los Angeles, CA 90095 USA
[2] Univ Southern Calif, Annenberg Sch Commun & Journalism, Los Angeles, CA 90089 USA
[3] London Sch Hyg & Trop Med, Dept Infect Dis Epidemiol, London WC1E 7HT, England
[4] Nagasaki Univ, Sch Trop Med & Global Hlth, Nagasaki 8528523, Japan
[5] Univ Calif Los Angeles, Dept Biostat, Los Angeles, CA 90095 USA
[6] Univ Calif Irvine, Dept Emergency Med, Irvine, CA 92617 USA
[7] Univ Calif Irvine, Dept Informat, Irvine, CA 92617 USA
[8] Fielding Sch Publ Hlth, Dept Epidemiol, 650 Charles E Young Dr S, Los Angeles, CA 90095 USA
[9] Univ Calif Irvine, Dept Emergency Med, 6091 Bren Hall, Irvine, CA 92617 USA