Immunohistopathology and platelet electron microscopy of ferrets infected with different influenza viruses. (A-D) Disease severity scoring of ferrets infected with A/H3N2 (blue), A/H1N1 (green), and A/H5N1 (red) virus at postinfection day 4. Median (n = 4) histopathology score (range 0-3). Error bars, SD. (E-F) Median (n = 4) histopathology score (range, 0-1). (G-I) Virus titer in homogenized organs (heart, liver, and spleen) at days 0.5, 1, and 4. Mean (n = 4). Error bars, SD. Dotted line represents the lower limit of detection. Adapted from Van den Brand et al³⁹  with permission. (J-K) Virus particle internalization (∼120 nm; red arrows) by platelets isolated from the blood drawn from a 2009 A/H1N1 virus-infected ferret. Red arrows: viruses. TEM original magnification ×20 000 (J); ×50 000 (K). The bars represent 250 nm. (L) Internalization of A/PR/8/34 virus by human platelets at 1, 5, and 20 minutes of incubation. The bars bar represent 250 nm.