CXCL8 and infection: To compare cytokine responses in ducks infected with SS-10 and NH-10, the expression of pro-inflammatory cytokines (IL-1β, IL-6), chemokine (IL-8), Th1-involved cytokine (IL-2), and IFN types I and II (IFN-alpha, IFN-beta, and IFN-gamma) in the lungs and thymus of ducks were tested during early-phase post-infection.