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Figure 1. A) Human incidence map for West Nile virus (WNV) early
in the transmission season, 2003, based on raw data. Incidence rates were
calculated by using the number of new human cases of WNV per county through
August 13, 2003, reported to the ArboNet surveillance network. High risk
is defined as incidence >1 case per 1 million inhabitants. B) Model-estimated
human incidence map for WNV in 2003. Expected risk was derived from the
observed incidence rates from August 13, 2003. High risk is defined as
incidence >1 case per million persons. C) Observed human risk for WNV
late in the transmission season, 2003. Incidence rates were calculated
by using the number of new human cases of WNV per county through October
1, 2003. High risk is defined as incidence >1 case per 100,000. This
risk surface served to compare the predictive ability of the (A) raw versus
(B) modeled early season disease maps.
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