The survey of H5N1 flu virus in wild birds in 14 Provinces of China from 2004 to 2007.
BACKGROUND
The highly pathogenic H5N1 avian influenza emerged in the year 1996 in Asia, and has spread to Europe and Africa recently. At present, effective monitoring and data analysis of H5N1 are not sufficient in Chinese mainland.


RESULTS
During the period from April of 2004 to August of 2007, we collected 14,472 wild bird samples covering 56 species of 10 orders in 14 provinces of China and monitored the prevalence of flu virus based on RT-PCR specific for H5N1 subtype. The 149 positive samples involved six orders. Anseriformes had the highest prevalence while Passeriformes had the lowest prevalence (2.70% versus 0.36%). Among the 24 positive species, mallard (Anas platyrhynchos) had the highest prevalence (4.37%). A difference of prevalence was found among 14 provinces. Qinghai had a higher prevalence than the other 13 provinces combined (3.88% versus 0.43%). The prevalence in three species in Qinghai province (Pintail (Anas acuta), Mallard (Anas platyrhynchos) and Tufted Duck (Aythya fuligula)) were obviously higher than those in other 13 provinces. The results of sequence analysis indicated that the 17 strains isolated from wild birds were distributed in five clades (2.3.1, 2.2, 2.5, 6, and 7), which suggested that genetic diversity existed among H5N1 viruses isolated from wild birds. The five isolates from Qinghai came from one clade (2.2) and had a short evolutionary distance with the isolates obtained from Qinghai in the year 2005.


CONCLUSIONS
We have measured the prevalence of H5N1 virus in 56 species of wild birds in 14 provinces of China. Continuous monitoring in the field should be carried out to know whether H5N1 virus can be maintained by wild birds.
Kou
Zheng
Z
State Key Laboratory of Virology, Wuhan Institute of Virology, Chinese Academy of Sciences, Wuhan, China.
Li
Yongdong
Y
Yin
Zuohua
Z
Guo
Shan
S
Wang
Mingli
M
Gao
Xuebin
X
Li
Peng
P
Tang
Lijun
L
Jiang
Ping
P
Luo
Ze
Z
Xin
Zhi
Z
Ding
Changqing
C
He
Yubang
Y
Ren
Zuyi
Z
Cui
Peng
P
Zhao
Hongfeng
H
Zhang
Zhong
Z
Tang
Shuang
S
Yan
Baoping
B
Lei
Fumin
F
Li
Tianxian
T
D025041:Animal Migration; D000818:Animals; D000835:Animals, Wild; D001717:Birds / Q000821:virology; D002681:China; D004372:Ducks / Q000821:virology; D005843:Geography; D053124:Influenza A Virus, H5N1 Subtype / Q000378:metabolism*; D005585:Influenza in Birds / Q000453:epidemiology* / Q000821:virology*; D010802:Phylogeny; D015995:Prevalence; D020133:Reverse Transcriptase Polymerase Chain Reaction; D017422:Sequence Analysis, DNA; D013045:Species Specificity