[1] Ctr Dis Control & Prevent, Arboviral Dis Branch, Div Vector Borne Infect Dis, Publ Hlth Serv,US Dept Hlth & Human Serv, Ft Collins, CO 80521 USA
[2] Columbia Univ, Coll Phys & Surg, Dept Med, New York, NY 10032 USA
[3] Colorado State Univ, Dept Microbiol Immunol & Pathol, Ft Collins, CO 80523 USA