Pathogenicity of human and avian H5N1 influenza viruses in ferrets

Virus and originGenotypeSeverity of diseaseNo. dead/ total no.Clinical signsVirus titera
Relative inactivity indexbWeight change (%)cT increase (°C)cNasal washes on indicated day postinfectionInternal organs
  • a Ferrets were inoculated with 106 EID50 of H5N1/04 viruses. Values are mean virus titers (log10 EID50/ml) for two to three ferrets, as determined in nasal washes or internal organs at three to seven days postinfection. Tissue samples (∼0.5 g) were collected and homogenized in 1 ml of sterile PBS with antibiotics. The lower limit of virus detection was <1 log10 EID50 per 1.0 ml of nasal wash or tissue homogenate. <, titer of <1.0 log10 EID50/ml; NA, not applicable (all ferrets in the group were dead); ND, not done, since there was no pathogenicity.

  • b Determined from observations over 7 days, as described previously (25). The relative inactivity index before H5N1/04 virus infection was 0; all ferrets were alert and playful.

  • c Maximal change in weight or temperature.

  • d Value for one animal.