Unadjusted incidence rate ratios (IRR) for the crude bivariate associations between human WNV and the landscape variables.

These associations are derived from Poisson models, with county and year as the panel levels. Model 1 is comprised of precipitation as the single independent variable, Model 2 is comprised of temperature as the single independent variable, and Model 3 is comprised of hydrogeographic area as the single independent variable.1Precipitation is the total monthly precipitation accumulation in centimeters from May through October.2Temperature is the monthly-weighted seasonal cumulative temperature in degrees Celsius.