Table 1.

Characteristics of influenza A H5N1 viruses

VirusGroupaCase descriptionPassage no.Infectivity titer (log10/ml)bMID50cLD50d
Age (yr)/genderOutcomeMDCKEggsTCID50EID50
HK/483B13/femaleFatal138.59.02.22.4
HK/485B24/femaleSevere/recovered228.58.71.12.9
HK/156A3/maleFatal037.710.03.25.9
HD/486A5/femaleMild/recovered248.79.01.2>7
X-31 (H3N2)NAe NA0>107.38.50.7>5.2
  • a Antigenic/genetic group of H5N1 viruses isolated from humans (3).

  • b Calculated by the method of Reed and Muench (24) from the results of serial titrations of viruses in MDCK cells and embryonated eggs.

  • c Expressed as the EID50 required to give 1 MID50.

  • d Expressed as the EID50 required to give 1 LD50.

  • e NA, not applicable.