[1] Ctr Dis Control & Prevent, Div Vector Borne Infect Dis, Ft Collins, CO 80521 USA
[2] Univ Calif Davis, Ctr Vector Borne Dis, Davis, CA 95616 USA
[3] Univ Calif Davis, Dept Pathol Microbiol & Immunol, Sch Vet Med, Davis, CA 95616 USA
[4] Univ Texas Med Branch, Dept Pathol, Ctr Emerging Infect Dis & Biodef, Inst Human Infect & Immun, Galveston, TX USA
[5] Univ Texas Med Branch, Dept Microbiol & Immunol, Ctr Emerging Infect Dis & Biodef, Inst Human Infect & Immun, Galveston, TX USA
[6] US Fish & Wildlife Serv, Div Migratory Bird Management, Portland, OR USA
[7] Colorado State Univ, Dept Biomed Sci, Ft Collins, CO 80523 USA