AI virus is a respiratory virus, so for this reason, of course, air plays an important role on the diffusion of the virus. This is more relevant when you have a big number of animals in a limited space (barn, farm and region too). It means that the direct, or in any case, strict contact between infected and healty birds is relevant. But the recent (2021-2022 epidemic) events showed as that the forced air ventilation system, very common now in poultry farms (in Italy basically in broiler and laying hens farms) means the passive spread on the area around the infected farm of a very huge quantity of virus and so if there are many farms one close to the other this could be the possible origin of the infection. It happened during the 2021-2022 epidemic that this passive spread of AI virus involved farms that were around 1 km far from an outbreak.