FIG 3.

Weight loss in ferrets challenged with H5N1 after exposure to seasonal influenza virus strains. Ferrets were first infected with H1N1pdm09 (Mex/09) (A) or H3N2 (Vic/11) (B) virus, allowed to recover for 1 (black squares) or 3 (gray circles) months, and then challenged with H5N1 (VN/04) virus along with a group of naive ferrets (open circles). Weight loss was assessed daily following H5N1 viral challenge. Ferrets that lost substantial amounts of body weight and were in extremis were euthanized. Ferrets challenged after 1 month of recovery from H1N1pdm09 infection did not experience weight loss, while those challenged 3 months after H1N1 infection showed weight loss after 6 DPI. For H3N2 virus preexposure, ferrets challenged 3 months later showed severe weight loss, while those infected with H5N1 virus 1 month later showed minimal weight loss followed by weight recovery.