BALB/c mice were lightly anesthetized and inoculated i.n. with 50 ml 10 2.5 pfu SD/09 virus in PBS. Mock-infected animals were inoculated i.n. with 50 ml PBS. At the indicated time, infected mice were sacrificed, and the parameters that present the course of the disease were determined. Twenty mice (10 infected with SD/09 virus and 10 inoculated with PBS) were used to investigate clinical signs and mortality for 14 days.