Table 1.

Transmissibility of influenza viruses in BALB/c mice

Experiment no.VirusSubtypeInoculated mice
Contact mice*
Weight loss, % Nose titers Lung titers Seroconversion (HI antibody titer range) § Virus detected in nose or lung Seroconversion
1Tx/91H1N12.72.4 ± 0.9 (2)3.6 ± 0.3 (3)4/4 (40–160)(0/3)0/3
1WSNH1N124.43.4 ± 0.5 (3)7.0 ± 0.4 (3)ND (0/3)0/3
11918H1N122.32.1 ± 0.8 (2)7.5 ± 0.3 (3)ND (0/3)0/3
2HK/8/68H3N212.42.2 ± 0.7 (2)4.2 ± 0.4 (3)4/4 (40–80)(0/3)0/3
2VN/1203/04H5N121.55.8 ± 0.4 (3)6.8 ± 0.4 (3)ND (0/3)0/3
21918H1N118.91.7 ± 0.4 (1)5.6 ± 0.3 (3)4/4 (80–160)(0/3)0/3
  • In experiment 1, groups of BALB/c mice (n = 7) were inoculated intranasally with 106 pfu of the indicated virus. In experiment 2, groups of BALB/c mice (n = 7) were inoculated intranasally with 103 pfu of the indicated virus. HI, hemagglutination inhibition; ND, not determined.

  • *Age-matched BALB/c mice (n = 3) were added to the same cage at 24 h p.i. No weight loss was observed in contact mice.

  • The percentage of mean maximum weight loss is shown (four mice per group).

  • Average tissue titers of three mice on day 4 p.i. expressed as 50% egg infectious dose/ml ± SD. The no. of positives is indicated in parentheses.

  • §Serum was collected on day 21 p.i., and homologous virus was used with horse RBCs for H5 virus or turkey RBCs for all other viruses in HI assays. The range of antibody titers obtained is indicated in parentheses.

  • Not determined because the four inoculated mice did not survive beyond 8 days p.i.