This pattern of IFN-β promoter activation was not due to examination of GFP expression too early or too late in infection since it was observed over a time course of Ud-Δ99/R38A infection: by 8 h p.i., the majority of cells were positive for viral NP and GFP-positive cells could be detected in small numbers (Fig. 2). The gene discussed is IFNB1; the disease is infection.