Table 1. Virulence and transmission of four HPAI H5N1 viruses in young mallard ducks.
| Duck group* | Challenge virus† | H5 clade | Morbidity/ mortality‡ | Mean day of shedding onset§ | Mean day of symptom onset|| | Day of death¶ | Mean shedding duration# | Mean peak titre** | Cumulative mean virus shedding†† | HI titre‡‡ | Productively. infected |
|---|---|---|---|---|---|---|---|---|---|---|---|
| D | HK1161 | 2.3.2.1b | 25/100 | 1.0±0.0 | 2.8±0.3 | 2, 3, 3, 4 | 2.0±0.4 | 7.5±0.1 (3) | 11.4±2.5 | na | 4/4 |
| Bulg38WB | 2.3.2.1c | 100/0 | 1.0±0.0 | 4.3±0.3 | –, –, –, – | 7.0±0.5 | 4.8±0.5 (3) | 26.3±2.8 | 55±15 (4/4) | 4/4 | |
| LaoLH2 | 2.3.4.1 | 100/75 | 1.0±0.0 | 4.5±0.3 | 5, 5, 7, – | 5.1±0.7 | 6.0±0.4 (3) | 24.2±2.2 | 80 (1/1) | 4/4 | |
| HKAP156 | 2.3.4 | 33/33 | 2.0±0.7 | 4 | 7, –, – | 3.8±2.1 | 2.6±1.0 (3) | 9.4±2.1 | 53±13 (3/3) | 3/3 | |
| DC | HK1161 | 2.3.2.1b | 50/100 | 2.3±0.3 | 4.5±0.6 | 3, 4, 5, 7 | 2.5±0.7 | 6.1±1.4 (5) | 12.8±3.0 | na | 4/4 |
| Bulg38WB | 2.3.2.1c | 100/25 | 3.0±0.7 | 6.5±0.6 | 9, –, –, – | 7.6±0.7 | 4.9±0.3 (7) | 29.4±1.2 | 25±15 (2/3) | 4/4 | |
| LaoLH2 | 2.3.4.1 | 75/75 | 2.5±0.5 | 6.0±0.4 | 5, 8, 8, – | 4.8±0.8 | 5.1±0.3 (5) | 19.7±2.1 | 40 (1/1) | 4/4 | |
| HKAP156 | 2.3.4 | 25/0 | 3.7±0.3# | 3 | –, –, –, – | 1.7±0.6 | 1.6±0.9 (5) | 4.0±2.0 | 40±0 (2/4) | 3/4 | |
| AC | HK1161 | 2.3.2.1b | 25/100 | 3.3±0.5 | 5.3±0.5 | 4, 6, 6, 6 | 2.3±0.6 | 5.5±0.7 (6) | 9.9±1.7 | na | 4/4 |
| Bulg38WB | 2.3.2.1c | 75/25 | 4.0±1.0# | 10.5±2.5 | 9, –, –, – | 5.1±1.8 | 5.0±0.5 (9) | 18.9±6.4 | 170±150 (2/3) | 3/4 | |
| LaoLH2 | 2.3.4.1 | 50/50 | 5.3±1.2 | 7.8±0.3 | 10, 14, –, – | 3.4±1.1 | 4.4±0.6 (9) | 15.1±5.0 | 40 (1/2) | 4/4 | |
| HKAP156 | 2.3.4 | 0/0 | 5.3±0.3# | na | –, –, –, – | 2.3±1.2 | 1.6±0.9 (7) | 4.8±2.3 | 20 (1/4) | 3/4 | |
| D | HK1161 Bulg38WB | 2.3.2.1 | 63/50 | 1.0±0.0 | – | – | 4.5±1.0 | 6.0±0.6 (3) | 18.9±3.3 | – | 8/8 |
| LaoLH2 HKAP156 | 2.3.4 | 63/50 | 1.5±0.4 | – | – | 3.9±1.0 | 4.3±0.8 (3) | 16.8±3.1 | – | 7/7 | |
| DC | HK1161 Bulg38WB | 2.3.2.1 | 75/63 | 2.6±0.4 | – | – | 5.1±1.1 | 4.8±0.7 (5) | 21.1±3.5 | – | 8/8 |
| LaoLH2 HKAP156 | 2.3.4 | 50/38 | 3.0±0.4 | – | – | 2.9±0.8 | 3.4±0.8 (5) | 11.9±3.3 | – | 7/8 | |
| AC | HK1161 Bulg38WB | 2.3.2.1 | 50/63 | 3.6±0.5 | – | – | 3.7±1.0 | 3.8±1.3 (9) | 14.4±3.5 | – | 7/8 |
| LaoLH2 HKAP156 | 2.3.4 | 25/25 | 5.3±0.6 | – | – | 2.3±0.7 | 2.1±0.7 (7) | 9.9±3.2 | – | 7/8 |
*D, donor (inoculated) animals; DC, direct-contact animals; AC, aerosol-contact animals.
†Abbreviations as in Methods.
‡In per cent; morbidity as detected via conjunctivitis, depression, or neurological symptoms (ataxia, seizure, disorientation); some animals died/were found dead without symptoms having been observed.
§Mean day p.i. ± standard error. Limit of detection was 0.75 log10 EID50 ml−1. # one animal in the group did not shed.
||Mean day p.i. ± standard error. For mean day of symptom onset, death was included as a symptom.
¶Either found dead in cage or euthanized due to moribund state.
#Shown are days ± standard error for oropharyngeal shedding. Swabs were titrated every day or every other day; we considered that a bird that shed from day 1 to day 5 but not on day 7 and with no data for day 6 shed 4.5 days. Birds that did not shed were excluded from the shedding duration calculation.
**In log10 EID50 ml−1. Limit of detection was 0.75 log10 EID50 ml−1. (Day of peak titre p.i.)
††Cumulative mean virus shedding over time (area under the curve) as log10 EID50 of oropharyngeal swabs.
‡‡Mean haemagglutination inhibition titre to homologous antigen ± standard error (animals with HI titre ≥10/surviving animals).
§§By virus shedding and/or seroconversion.