[1] Univ Calif San Francisco, Dept Neurosurg, San Francisco, CA 94143 USA
[2] Med Coll Wisconsin, Dept Neurosurg, Milwaukee, WI 53226 USA
[3] Univ Calif San Francisco, Dept Hosp Epidemiol & Infect Control, San Francisco, CA 94143 USA
[4] Univ Washington, Fred Hutchinson Canc Res Inst, Vaccine & Infect Dis Div, Seattle, WA 98195 USA
[5] Univ Washington, Div Allergy & Infect Dis, Seattle, WA 98195 USA