Volume 14, Number 11—November 2008
Letter
Incubation Period for Human Cases of Avian Influenza A (H5N1) Infection, China
Yang Huai, Nijuan Xiang, Lei Zhou, Luzhao Feng, Zhibin Peng, Robert S. Chapman, Timothy M. Uyeki, and Weizhong Yang
Table
Estimated incubation period of 24 human cases of infection with avian influenza A virus (H5N1), China*
| Exposure data | Case-patients with exposure to sick/ dead poultry only | Case-patients with exposure to wet poultry market only | p value | All case-patients |
|---|---|---|---|---|
| No. case-patients with exposures on multiple days | 12 | 6 | 18 | |
| Overall median incubation period, d (range) | 4.5 (2–9.5) | 6.3 (3.5–7) | 0.276 | 5 (2–9.5) |
| Median of minimum incubation period, d (range) | 1 (0–5) | 0 (0–2) | 0.315 | 0.5 (0–5) |
| Median of maximum incubation period, d (range) |
7.5 (4–14) |
11.5 (7–14) |
0.108 |
8.5 (4–14) |
| No. case-patients with single known exposure | 4 | 2 | 6 | |
| Overall median incubation period, d (range) |
3.5 (2–6) |
8.5 (8–9) |
0.064 |
5 (2–9) |
| All case-patients | 16 | 8 | 24 | |
| Overall median incubation period, d (range) | 4.3 (2–9) | 7 (3.5–9) | 0.045 | 5 (2–9.5) |
| Overall median of minimum incubation period, d (range) | 1.5 (0–6) | 1 (0–9) | 0.752 | 1.5 (0–9) |
| Overall median of maximum incubation period, d (range) | 6 (2–14) | 9 (7–14) | 0.031 | 7.5 (2–14) |
*Boldface represents significant results (Wilcoxon rank-sum test).
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