Figure 4. Global and local predicted spreading patterns of chikungunya virus, Carabobo state, Venezuela, 2014. A) Contour map (global scale) of the predicted spreading waves and the velocity vector arrows of each case of chikungunya. The contour map and contour lines in black (traveling waves) were estimated by the best-fit trend surface analysis (third order polynomial model) of time (days) to the first reported case or index case of chikungunya across the landscape. White lines correspond to the road system of the area. The background gradient of color shows the probability of chikungunya virus diffusion according to the prediction of the model: the darker the red, the higher the probability of spread. Each vector (blue outlined arrows) represents the instantaneous velocity derived from the partial, differential equations from the trend surface analysis model (Appendix). B) Spatial prediction map for the ordinary kriging (Gaussian model) interpolation of the time (each color represents a different number of days) of chikungunya spread. Contour lines from trend surface analysis depicted in the kriging surface are shown only for comparison purposes. Yellow star indicates index case; green diamond indicates first autochthonous case.