time points. At days 4, 5 and 6 after WNV infection, we detected virus in the brains of 67%, 78% and 83% of mice, respectively (Fig. 3d) . A single 500 µg dose of E16 or E34 at day 4 resulted in an 80-90% survival rate (Fig. 3e) . A single 2 mg dose of E16 at day 5 resulted in 90% survival (Fig. 3f) and complete clearance of WNV from the brain in 68% of mice by day 9 (Fig. 3g) . Thus, administration of neutralizing monoclonal antibodies to mice with active CNS infection improved survival and induced a virologic cure. As expected, lengthening the interval before treatment was associated with decreased benefit. Administration of E16 at day 6 did not enhance survival (data not shown), although average survival time was increased (9.5 d ± 0.4 to 11.5 d ± 0.4; P = 0.003).