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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 Hongjie YuComments to Author 
Author affiliations: Chinese Center for Disease Control and Prevention, Beijing, People’s Republic of China (Y. Huai, N. Xiang, L. Zhou, L. Feng, Z. Peng, H. Yu); Chulalongkorn University, Bangkok, Thailand (Y. Huai, R.S. Chapman); Centers for Disease Control and Prevention, Atlanta, Georgia, USA (T.M. Uyeki);

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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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