Male Fitch ferrets (Triple F Farms), 7 to 10 months old and serologically negative by hemagglutination inhibition to currently circulating influenza viruses, were used in this study. Ferrets were housed in a Duo-Flow Bioclean mobile clean room (Lab Products) for the duration of each experiment. Intranasal (i.n.) inoculations were performed under anesthesia as previously described using 10 6 EID 50 of virus diluted in PBS in a 1 ml or 100 ml volume [29] . Ocular (i.o.) inoculations were performed under anesthesia using 10 6 EID 50 of virus diluted in PBS in a 100 ml or 20 ml volume. Virus inoculum was administered dropwise to the surface of the right eye of each ferret and massaged over the surface of the eye by the eyelid.