Table 1. Studies of H5N1 influenza in grazing ducks in Thailand, February to July 2004*.
| Flock no. | Approximate no. ducks | Age when positive for H5N1 virus (d) | Duration of virus shedding before detection of illness or culling (d) | Highest viral titer (log10 EID50/mL) | Antibody titers to H5N1 (HI) (log2) before culling |
|---|---|---|---|---|---|
| 1† | 4,600 | 66 | 8 | 2.0 | <1‡ |
| 2§ | 5,200 | 78 | 10 | 3.1 | 2 |
| 3† | 8,000 | 42 | 5 | 2.0 | <1 |
| 4† | 6,800 | 74 | 7 | 2.5 | 2 |
| 5† | 4,300 | 93 | 5 | 3.3 | 2 |
| 6¶ | 7,200 | 59 | 5 | 3.6 | 2 |
| 7¶ | 10,000 | 82 | 7 | ND | ND |
| 8† | 6,300 | 60 | 9 | 3.8 | 2 |
| 9† | 9,800 | 71 | 10 | ND | ND |
| 10† | 5.500 | 51 | 6 | 3.4 | ND |
*EID50, 50% egg infectious dose; HI, hemagglutination inhibition; ND, not done. †Suphanburi Province. ‡Serum samples collected ≈12 d after flock moved to rice field. §Nakornpathom Province. ¶Ayuthdhaya Province.