In the brains infected with Pigeon04, mRNA expression levels of Mx1, OAS, IL6, IL1β and CCL5 were at least 17 fold higher than those of respective genes in the infected lungs on day 5 post infection when this virus almost similarly replicated in the lungs and brains (Table 2, Figs. 2 and 3). This evidence concerns the gene IL1B and infection.