Rubella epidemics and genotypic distribution of the rubella virus in Shandong Province, China, in 1999-2010.
BACKGROUND
The rubella vaccine was introduced into the immunization program in 1995 in the Shandong province, China. A series of different rubella vaccination strategies were implemented at different stages of measles control in Shandong province.


RESULTS
The average reported incidence rate of rubella cases remained at a low level in Shandong province after 1999. However, rubella epidemics occurred repeatedly in 2001/2002, 2006, and 2008/2009. The age of the onset of rubella cases gradually increased during 1999-2010, which showed that most cases were found among the 10 years old in 1999 and among the 17 years old in 2010. Phylogenetic analysis was performed and a phylogenetic tree was constructed based on the World Health Organization standard sequence window for rubella virus isolates. All rubella viruses isolated in Shandong province were divided into 4 genotypes: 1E, 1F, 2A, and 2B. Genotype 1E viruses accounted for the majority (79%) of all these viruses. The similarity of nucleotide and amino acid sequences among genotype 1E viruses was 98.2-100% and 99.1-100%, respectively. All Shandong genotype 1E strains, differed from international genotype 1E strains, belonged to cluster 1 and interdigitated with the viruses from other provinces in mainland China. The effective number of infections indicated by a bayesian skyline plot remained constant from 2001 to 2009.


CONCLUSIONS
The gradual shift of disease burden to an older age group occurred after a rubella-containing vaccine was introduced into the childhood immunization schedule in 1995 in Shandong province. Four genotypes, including 1E, 1F, 2A, and 2B, were found in Shandong province during 2000-2009. Genotype 1E, rather than genotype 1F, became the predominant genotype circulating in Shandong province from 2001. All Shandong genotype 1E viruses belong to the genotype 1E/cluster 1; they have constantly circulated, and co-evolved and co-circulated, with those from other provinces.
Shandong Provincial Key Laboratory for Infectious Disease Control and Prevention, Shandong Center for Disease Control and Prevention, Jingshi Road, Jinan, People's Republic of China.
Changyin
C
Wang
Zhen
Z
Zhu
Qing
Q
Xu
Aiqiang
A
Xu
Xueqiang
X
Fang
Lizhi
L
Song
Weixiu
W
Li
Ping
P
Xiong
Wenbo
W
Xu
D000293:Adolescent; D000328:Adult; D017677:Age Distribution; D001483:Base Sequence; D001499:Bayes Theorem; D002648:Child; D002681:China / Q000453:epidemiology; D058872:Epidemics / Q000706:statistics & numerical data*; D005838:Genotype; D006306:Health Surveys / Q000706:statistics & numerical data; D006801:Humans; D010802:Phylogeny; D012409:Rubella / Q000453:epidemiology* / Q000821:virology*; D012412:Rubella virus / Q000235:genetics* / Q000302:isolation & purification; D014944:World Health Organization; D055815:Young Adult