Risk factors for human illness with avian influenza A (H5N1) virus infection in China.
BACKGROUND
In China, 30 human cases of avian influenza A (H5N1) virus infection were identified through July 2008. We conducted a retrospective case-control study to identify risk factors for influenza H5N1 disease in China.


METHODS
A questionnaire about potential influenza H5N1 exposures was administered to 28 patients with influenza H5N1 and to 134 randomly selected control subjects matched by age, sex, and location or to proxies. Conditional logistic regression analyses were performed.


RESULTS
Before their illness, patients living in urban areas had visited wet poultry markets, and patients living in rural areas had exposure to sick or dead backyard poultry. In multivariable analyses, independent risk factors for influenza H5N1 were direct contact with sick or dead poultry (odds ratio [OR], 506.6 [95% confidence interval {CI}, 15.7-16319.6]; P<.001), indirect exposure to sick or dead poultry (OR, 56.9 [95% CI, 4.3-745.6]; P=.002), and visiting a wet poultry market (OR, 15.4 [95% CI, 3.0-80.2]; P=.001).


CONCLUSIONS
To prevent human influenza H5N1 in China, the level of education about avoiding direct or close exposures to sick or dead poultry should be increased, and interventions to prevent the spread of influenza H5N1 at live poultry markets should be implemented.
Office for Disease Control and Emergency Response, National Institute for Viral Disease Control and Prevention, Chinese Center for Disease Control and Prevention, Beijing, China.
Lei
L
Zhou
Qiaohong
Q
Liao
Libo
L
Dong
Yang
Y
Huai
Tian
T
Bai
Nijuan
N
Xiang
Yuelong
Y
Shu
Wei
W
Liu
Shiwen
S
Wang
Pengzhe
P
Qin
Min
M
Wang
Xuesen
X
Xing
Jun
J
Lv
Ray Y
RY
Chen
Zijian
Z
Feng
Weizhong
W
Yang
Timothy M
TM
Uyeki
Hongjie
H
Yu
D000293:Adolescent; D000328:Adult; D016022:Case-Control Studies; D002681:China / Q000453:epidemiology; D004781:Environmental Exposure; D005260:Female; D006801:Humans; D053124:Influenza A Virus, H5N1 Subtype; D007251:Influenza, Human / Q000453:epidemiology* / Q000821:virology*; D008297:Male; D011159:Population Surveillance; D012307:Risk Factors; D055815:Young Adult