Distinct risk profiles for human infections with the Influenza A(H7N9) virus among rural and urban residents: Zhejiang Province, China, 2013.
OBJECTIVE
To identify the risk factors and source of infection leading to human infections with the Influenza A(H7N9) virus in urban and rural areas.


METHODS
We conducted a case-control investigation to identify potential exposures and risk factors. Controls were randomly selected from the same community as the cases using random digit dialing. We used exact conditional logistic regression to evaluate the exposures and risk factors, stratified by urban and rural residence.


RESULTS
Buying live or freshly slaughtered poultry from a market was significantly associated with illness onset among both urban [48% of 25 case-patients and 12% of 125 control-persons, adjusted odds ratio (AOR) = 19, 95% CI: 2.3-929] and rural (33% of 18 case-patients and 8.9% of 90 control-persons, AOR = 13, 95% CI:1.5-∞) residents. In rural area, tending to home-raised poultry (56% of 18 case-patients and 10% of 90 control-persons, AOR = 57, 95% CI: 7.5-∞) and existence of a poultry farm in the vicinity of the residence (28% of 18 case-patients and 5.6% of 90 control-persons, AOR = 37, 95% CI: 3.8-∞) were also significantly associated with disease onset. Presence of underlying medical conditions was a significant risk factor for urban residents (76% of 25 case-patients and 13% of 125 control-persons, AOR = 49, 95% CI: 7.1-2132).


CONCLUSIONS
Buying live or freshly slaughtered poultry from a market is a risk factor for both urban and rural residents, tending to home-raised poultry and existence of a poultry farm in the vicinity of the residence are risk factors unique for rural residents. The virus might have been in stealth circulation in the poultry population before infecting humans. We recommend strict poultry market management and multisectoral collaboration to identify the extent of poultry infection in China.
Zhejiang Provincial Center for Disease Control and Prevention, Hangzhou, People's Republic of China.
Fan
F
He
Chinese Field Epidemiology Training Program, Chinese Center for Disease Control and Prevention, Beijing, People's Republic of China; Dongguan Municipal Center for Disease Control and Prevention, Dongguan City, People's Republic of China.
Meng
M
Zhang
Zhejiang Provincial Center for Disease Control and Prevention, Hangzhou, People's Republic of China.
Xinyi
X
Wang
Zhejiang Provincial Center for Disease Control and Prevention, Hangzhou, People's Republic of China.
Haocheng
H
Wu
Zhejiang Provincial Center for Disease Control and Prevention, Hangzhou, People's Republic of China.
Xiaopeng
X
Shang
Zhejiang Provincial Center for Disease Control and Prevention, Hangzhou, People's Republic of China.
Fudong
F
Li
Zhejiang Provincial Center for Disease Control and Prevention, Hangzhou, People's Republic of China.
Chen
C
Wu
Zhejiang Provincial Center for Disease Control and Prevention, Hangzhou, People's Republic of China.
Junfen
J
Lin
Chinese Field Epidemiology Training Program, Chinese Center for Disease Control and Prevention, Beijing, People's Republic of China.
Bao-Ping
BP
Zhu
D000328:Adult; D017677:Age Distribution; D000368:Aged; D000369:Aged, 80 and over; D002681:China / Q000453:epidemiology; D002947:Cities / Q000453:epidemiology*; D005260:Female; D006801:Humans; D064766:Influenza A Virus, H7N9 Subtype / Q000502:physiology*; D007251:Influenza, Human / Q000453:epidemiology*; D016015:Logistic Models; D008297:Male; D008875:Middle Aged; D012306:Risk; D012424:Rural Population / Q000706:statistics & numerical data*; D017678:Sex Distribution