Abstract: To investigate the circulation and replication of H9N2 subtype avian influenza viruses ( AIVs) in live bird markets ( LBMs) in
China，a total of 12 635 swab samples were collected from 58 randomly selected LBMs in Shanghai，Jiangsu，Anhui and Guangdong in 2014，and were detected by virus isolation，ＲT － PCＲ and sequencing． The 12635 swab samples ( 15. 11%) in 58 LBMs ( 98. 28%) were found to
be H9N2 AIV positive． The prevalence of the virus in chicken，duck，goose and pigeon samples were22. 98% ( 1730 /7529) ，3. 62% ( 94 /
2594) ，4. 08% ( 67 /1643) and 2. 09% ( 18 /861) ，respectively，and the prevalence of the virus in Shanghai，Jiangsu，Anhui and Guangdong
samples were 24. 11% ( 688 /2853) ，8. 43% ( 284 /3368) ，15. 27% ( 475 /3110) ，13. 95% ( 461 /3304) ，respectively． The virus
prevalence in retail LBMs ( 34. 40%) was significantly higher than that of whole － sale LBMs ( 12. 24%) ． The virus prevalence increased
from 11. 45% in the birds having been staying in whole － sale markets less than 8 hr to 29. 13% in the birds having been staying in whole －
sale markets more than 48 hr． Phylogenetic analysis suggested that all the H9N2 AIVs identified in this study belonged to the dominant clade
( h9. 4. 2. 5) of H9N2 AIVs circulating in China． These results of epidemiological surveys suggested that H9N2 AIVs widely circulated in the
birds ( especially chickens) of LBMs in China，and the virus actively spread and replicated among the birds in LBMs with their staying in
whole － sale LBMs and transferring from whole － sale LBMs to retail LBMs．