TABLE 1.

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
357LungsBrainSpleenIntestine
Human
    A/Vietnam/1203/04ZSevere2/22.7−30.62.85.35.5dNA5.56.02.03.3
    A/Thailand/1(Kan-1)/04ZSevere2/21.9−19.42.23.64.65.3d3.05.3<<
    A/Vietnam/3062/04ZSevere1/21.4−10.21.75.84.0d4.0d4.54.82.53.5
    A/Vietnam/3046/04ZSevere1/21.9−18.82.23.81.5<<<<<
Avian
    A/quail/Vietnam/36/04ZSevere2/22.1−17.31.44.34.85.83.51.02.32.3
    A/duck/Thailand/71.1/04ZSevere1/21.9−14.81.64.13.53.03.35.52.53.3
    A/chicken/Vietnam/39/04ZMild0/21.0−9.30.63.41.8<NDNDNDND
    A/chicken/Vietnam/C58/04ZMild0/31.0−3.00.62.6<<<<<<
    A/chicken/Indonesia/5/04ZMild0/21.4−0.70.94.44.11.4<<<<
    A/chicken/Indonesia/MS/04ZMild0/21.0−8.00.54.23.41.0<<<<
    A/falcon/HK/D0028/04ZMild0/21.4+1.90.93.02.4<NDNDNDND
    A/duck/Hunan/1504/04ZMild0/21.4−1.80.6<<<NDNDNDND
    A/duck/Guanxi/1304/04ZMild0/21.7−8.30.83.03.5<<<<<
  • 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.