Figure 1. Summary of surveillance data indicating zoonotic and human transmission of West Nile virus (WNV) in Puerto Rico in 2007. Percentage of anti-WNV immunoglobulin (Ig) M–positive chickens per week from June 4 through December 20. Chickens were bled weekly during the beginning of transmission and monthly starting in September 2007. Sixty chickens were placed in the sentinel surveillance sites as previously described by Barrera et al. (7).
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