Interestingly, it has been reported by Van Reeth and Nauwynck [135] that a subclinical course of the infection together with a gross lung consolidation involving up to 34% of the investigated lungs at 4 days post infection (DPI) was associated with high levels of IFN-α, while TNF-α was negligible and IL-1 even undetectable. This evidence concerns the gene IFNA1 and infection.