Single Endemic Genotype of Measles Virus Continuously Circulating in China for at Least 16 Years

Abstract

The incidence of measles in China from 1991 to 2008 was reviewed, and the nucleotide sequences from 1507 measles viruses (MeV) isolated during 1993 to 2008 were phylogenetically analyzed. The results showed that measles epidemics peaked approximately every 3 to 5 years with the range of measles cases detected between 56,850 and 140,048 per year. The Chinese MeV strains represented three genotypes; 1501 H1, 1 H2 and 5 A. Genotype H1 was the predominant genotype throughout China continuously circulating for at least 16 years. Genotype H1 sequences could be divided into two distinct clusters, H1a and H1b. A 4.2% average nucleotide divergence was found between the H1a and H1b clusters, and the nucleotide sequence and predicted amino acid homologies of H1a viruses were 92.3%–100% and 84.7%–100%, H1b were 97.1%–100% and 95.3%–100%, respectively. Viruses from both clusters were distributed throughout China with no apparent geographic restriction and multiple co-circulating lineages were present in many provinces. Cluster H1a and H1b viruses were co-circulating during 1993 to 2005, while no H1b viruses were detected after 2005 and the transmission of that cluster has presumably been interrupted. Analysis of the nucleotide and predicted amino acid changes in the N proteins of H1a and H1b viruses showed no evidence of selective pressure. This study investigated the genotype and cluster distribution of MeV in China over a 16-year period to establish a genetic baseline before MeV elimination in Western Pacific Region (WPR). Continuous and extensive MeV surveillance and the ability to quickly identify imported cases of measles will become more critical as measles elimination goals are achieved in China in the near future. This is the first report that a single endemic genotype of measles virus has been found to be continuously circulating in one country for at least 16 years.

Molecular epidemiology of measles virus infection in Shanghai in 2000–2012: the first appearance of genotype D8

“…[12][13][14] MVs surveillance in China since 1993 revealed that the H1 genotype is the endemic dominant strain, which has H1a, H1b and H1c subtypes, with H1a being the dominant subtype circulating in China. 11,[15][16][17][18][19] To assist the goal of globally eliminating measles, it is important to carry out molecular epidemiology investigation besides classic epidemiology studies. Molecular epidemiology can support classical epidemiology by identifying transmission pathways and confirming whether the isolated virus genotype is consistent with the predominant genotype circulating in the country or whether it is an imported strain, and region from which the case was imported.…”

Monitoring progress towards the elimination of measles in China: an analysis of measles surveillance data

“…Since there is no non-human reservoir for measles, the circulation of this genotype represents person-toperson transmission that has persisted in China for at least 20 years. 23 The elimination of measles in China will require all of the remaining immunity gaps to be identified and filled -to the point that transmission of measles virus can no longer be sustained. If immunity gaps are to be identified and adequately filled, case investigation and outbreak analysis and response may all need to be improved.…”

Molecular Characterization of Wild Type Measles Virus from Adult Patients in Northern China, 2014

“…6 Based on phylogenetics analyses, genotype H1 MeVs are classified as 1) Cluster1 viruses (H1a), which comprise the most frequently detected strains since 2000, and 2) Cluster2 viruses (H1b), which have not been detected after 2005. [7][8][9][10] Previous reports suggested that immunization of populations with low vaccination coverage is vital since these populations represent a bigger public health risk than sporadic, susceptible individuals. 11 China initially implemented a two-dose measles vaccination program in 1986, where the first dose was administered to infants at 8 months of age, and the second dose at 7 years of age.…”