[1] Univ Colorado, Hlth Sci Ctr, Div Gen Internal Med, Denver, CO 80262 USA
[2] Univ Colorado, Hlth Sci Ctr, Dept Pediat, Div Infect Dis, Denver, CO 80262 USA
[3] Univ Colorado, Hlth Sci Ctr, Dept Prevent Med & Biometr, Denver, CO 80262 USA
[4] Univ Utah, Dept Med, Salt Lake City, UT 84112 USA