[1] Univ Calif San Diego, Dept Med & Pathol, La Jolla, CA 90293 USA
[2] Univ Calif San Diego, Dept Phys, La Jolla, CA 90293 USA
[3] Univ Zurich Hosp, Div Infect Dis, CH-8091 Zurich, Switzerland
[4] Univ Zurich Hosp, Hosp Epidemiol, CH-8091 Zurich, Switzerland
[5] San Francisco Gen Hosp, Posit Hlth Program, San Francisco, CA 94110 USA
[6] Univ Edinburgh, Sch Biol Sci, Edinburgh EH9 3JT, Midlothian, Scotland
[7] Bristol Myers Squibb Co, Wilmington, DE 19805 USA
[8] Vet Affairs San Diego Healthcare Syst, La Jolla, CA 92161 USA