Body temperatures, relative lung weights and lung viral titers of ferrets inoculated with different influenza viruses. The ferrets were intratracheally inoculated with seasonal H1N1 (n = 3), new H1N1 (n = 6) or highly pathogenic avian influenza (HPAI) H5N1 (n = 6)influenza viruses at a dose of 10⁶ median tissue culture infective dose (TCID₅₀). The increase in body temperature (A), the relative lung weight (B), and the lung viral titer (C) of the new H1N1 virus group were intermediate between those of the seasonal H1N1 virus group and that of the HPAI H5N1 virus group.