[1] Ctr Dis Control & Prevent, Div Vector Borne Dis, Ft Collins, CO 80521 USA
[2] Univ N Dakota, Sch Med & Hlth Sci, Grand Forks, ND 58201 USA
[3] Sanford Hlth, Fargo, ND USA
[4] Blood Syst Res Inst, San Francisco, CA USA
[5] Fargo Vet Affairs Med Ctr, Fargo, ND USA
[6] Wisconsin Dept Hlth, Madison, WI USA
[7] Univ Calif San Francisco, San Francisco, CA 94143 USA