[1] ST LOUIS UNIV, SCH MED, DEPT RADIOL, ST LOUIS, MO 63104 USA
[2] CTR DIS CONTROL, VIRAL & RICKETTSIAL & BACTERIAL ZOONOSES BRANCH, ATLANTA, GA 30333 USA
[3] CTR DIS CONTROL, VIRAL & RICKETTSIAL & BACTERIAL ZOONOSES BRANCH, FT COLLINS, CO 80522 USA