[1] Univ Calif San Francisco, Div Emergency Med, 550 16th St,Box 0649, San Francisco, CA 94158 USA
[2] Univ Utah, Primary Childrens Hosp, Dept Pediat, Sch Med, Salt Lake City, UT USA
[3] Univ Calif San Francisco, Dept Pediat, San Francisco, CA USA
[4] Univ Utah, Primary Childrens Hosp, Div Pediat Infect Dis, Sch Med, Salt Lake City, UT USA