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Volume 23, Number 8—August 2017

Preliminary Epidemiology of Human Infections with Highly Pathogenic Avian Influenza A(H7N9) Virus, China, 2017

Lei Zhou1, Yi Tan1, Min Kang1, Fuqiang Liu1, Ruiqi Ren1, Yali Wang, Tao Chen, Yiping Yang, Chao Li, Jie Wu, Hengjiao Zhang, Dan Li, Carolyn M. Greene, Suizan Zhou, A. Danielle Iuliano, Fiona Havers, Daxin Ni, Dayan Wang, Zijian Feng, Timothy M. Uyeki, and Qun LiComments to Author 
Author affiliations: Authr affiliations: Chinese Center for Disease Control and Prevention, Beijing, China (L. Zhou, R. Ren, Y. Wang, T. Chen, C. Li, D. Li, D. Ni, D. Wang, Z. Feng, Q. Li); Guangxi Center for Disease Control and Prevention, Nanning, China (Y. Tan, Y. Yang); Guangdong Center for Disease Control and Prevention, Guangzhou, China (M. Kang, J. Wu); Hunan Center for Disease Control and Prevention, Changsha, China (F. Liu, H. Zhang); Centers for Disease Control and Prevention, Atlanta, Georgia, USA (C.M. Greene, S. Zhou, A.D. Iuliano, F. Havers, T.M. Uyeki)

Main Article


Selected characteristics of case-patients with HPAI and LPAI A(H7N9) virus infections, mainland China, September 1, 2016–March 31, 2017*

Infection type
p value
HPAI, n = 8
LPAI, n = 553
Median age (range), y
56.5 (28–71)
57 (3–91)
Age group, y
0–14 0 5/553 (1) NA
15–59 5 (63) 313/553 (57)
3 (38)
235/553 (42)

M 4 (50) 400/553 (72) 0.317
4 (50)
153/553 (28)

Residence area‡
Urban 1 (13) 193/364 (53) 0.031§
7 (88)
171/364 (47)

Having >1 underlying medical conditions¶
5 (63)
234/432 (54)
Poultry exposure within 10 d of illness onset
Any exposure to poultry 8 (100) 442/500 (90) 1.000§
Visited live poultry market 3 (38) 324/442 (73) NA
Exposure to backyard poultry 4 (50) 98/442 (22) NA
Occupational exposure to poultry 1 (13) 20/442 (5) NA
Exposure to sick or dead poultry
4 (50)
43/268 (16)
Clinical management
Hospitalization 8 (100) 478/480 (99) NA
Antiviral treatment 8 (100) 392/404 (97) NA
ICU 7 (88) 323/403 (80) 1.000
Mechanical ventilation
6 (75)
221/386 (57)
Timeline of clinical management (median), d†
Illness onset to first medical service seeking 0.5 (0–5) 2 (0–34) 0.096
Illness onset to hospitalization 2.5 (0–5) 5 (0–35) 0.032
Illness onset to antiviral treatment 4 (1–8) 6 (0–29) 0.168
Illness onset to diagnosis 6.5 (4–9) 8 (0–31) 0.241
Illness onset to death
6.5 (5–44)
13 (2–62)
Death 4 (50) 203/376 (54) 1.000
Recovered and discharged 4 (50) 173/376 (46)

*Values are no. (%) unless otherwise indicated. The χ2 test was used to compare the variables between HPAI and LPAI groups. Data were missing for some variables, and data on final outcomes were missing for case-patients with LPAI A(H7N9) virus infection who remained hospitalized as of March 31, 2017. We were not able to perform the statistical analyses to assess differences for some variables because the number of cells with expected frequency of <5 was >20% and some cells had expected frequency of <1. HPAI, highly pathogenic avian influenza; ICU, intensive-care unit; LPAI, low pathogenic avian influenza; NA, not available.
†The z-test was used to compare median age and median days of the timeline of clinical management between HPAI and LPAI groups.
‡Urban was defined as cities, towns, and suburbs; rural was defined as villages and countryside (3).
§Residence area and “any exposure to poultry” were compared between HPAI and LPAI groups by using the Fisher exact test.
¶Three HPAI case-patients had chronic cardiovascular disease, and 2 HPAI case-patients had chronic metabolic disease.
#“Having >1 underlying medical conditions” and “exposure to sick or dead poultry” were compared between HPAI and LPAI groups by using the χ2 test for continuous correction.

Main Article

1These authors contributed equally to this article.

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Page updated: July 18, 2017
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