The PCR products were sequenced at Sangon (Shanghai, China). == Phylogenetic analysis and inference of the evolutionary distances == In this study, we obtained class I reference NDV F gene sequences representing previously class I genotypes 1 to 9 based on the previously established classification system and reference strains representing the newly established classification system as 1a, 1b and 1c from the Genbank, while the accession numbers of these NDVs were shown in the phylogenetic trees. was designated as sub-genotype 3c. When based on the new classification system, sub-genotype 3b was classified into sub-genotype 1a and the sub-genotype 3c was classified into sub-genotype 1b. Over 62% (21/34) of the viruses were chicken-origin and only 13 isolates were waterfowl-origin. The Cross-neutralization ERK2 reactions between CK/JS/05/11, CK/JS/06/12 and the vaccine strain LaSota showed significant antigenic differences between them. == Conclusions == Currently, sub-genotype 3c (or 1b) NDVs are the most frequently isolated classI strains at LBMs in Eastern China., and the class I NDVs has transferred from waterfowls to chickens and circulated in chicken flocks extensively. Keywords:Class I Newcastle disease virus, Sub-genotype 3c, Sub-genotype 1b, Genetic, Antigenticy == Background == Newcastle disease (ND) is caused by Newcastle disease virus(NDV)which has caused severe economic losses all around the world [1,2]. NDV is a member of avian paramyxovirus (APMV), which belongs to the genus Avulavirus, sub-familyParamyxovirinae, familyParamyxoviridae, and orderMononegavirales[3]. The genome of NDV is a single-stranded, negative-sense, nonsegmented RNA of approximately 15.2 kb. The viral genome is comprised of six genes: nucleocapsid (NP), phosphoprotein (P), matrix (M), fusion (F), hemagglutininneuraminidase (HN), and RNA-dependent RNA polymerase (L) [4]. The strains of NDV can be divided into two distinct clades: class I and class CTEP II, and based on the older classification system, both clades could be CTEP divided into 9 genotypes, and the class II clade can be divided into fifteen genotypes when based on the new classification system, while the class I clade can be divided into three sub-genotypes [57]. Liu et.al has found that the class I virus strains circulating among Eastern China were genotype 2 and 3, CTEP while the genotype 3 can be divided into two sub-genotype: 3a and 3b [8]. In 2012, one class I virus isolated in Eastern China was ascribed to genotype 4 [9], which means that the class I viruses circulating in Eastern China were mix. As Liu et al. [8] only concerned about the class I virus circulating in ducks at LBMs in Eastern China, and deals of chickens were also existed at the live bird markets (LBMs), however, CTEP the circulation of the class I virus among chickens has not been well elucidated. In this study, we collected 7106 cloacal swabs from 600 flocks including both chickens and waterfowls for virus isolation from 2008 to 2012 and 34 class I isolates were characterized phylogentically while and 15 of the 34 NDVs were pathologically characterized. == Results == == Isolation and identification of the NDVs from the LBMs in Eastern China == We obtained a total of 7106 samples by monthly collections from multiple avian species at LBMs in Eastern China during May 2008 to April 2012, and 247 NDVs were isolated and identified with a total isolation rate of 3.48%. As is shown in Table1, a total of 3.32% (236/7106) class I NDVs were identified and the isolation rates in colder months (from November to March) were higher than in warmer months (from April to October) which is consistent with the previous report [8]. Furthermore, the monthly isolation rate varied from 0 to 7.5% and the yearly isolation rate varied from 2.91% to 5.67% and January 2012 had the highest isolation rate although no specific thing about these times was found. The 236 class I NDVs were collected from 34 flocks (21 from the chickens and 13 from the waterfowls), and the details for these isolates were listed in Table2. == Table 1. == Monthly isolations of NDVs from cloacal swabs of multiple avian species at live bird CTEP markets for wholesale in Eastern China during May 2008 to April.