Foot-and-mouth disease is an economically important viral disease in animals. It is shown that airborne diffusion is one of the main sources of contamination between animals and between herds. Epidemiological data linked to viral particle excretion can thus be used in a predictive model, added to meteorological data related to the few days before the slaughter of animals. The model computes, on a 10 km radius around the outbreak and in every space direction, the quantity of viral particles that a sensitive animal could have breathed. The aim is to define a risk area, and, according to the number and size of farms in the surrounding, to give arguments for the best sanitary decision within the emergency plan.