Epidemiologic and genetic characteristics of mumps viruses isolated in China from 1995 to 2010.

The epidemiologic and genetic characteristics of mumps viruses detected in China from 1995 to 2010 were analyzed in this study. Mumps remains endemic in China with a high overall incidence rate. The incidence of mumps in Western China was higher than that in other regions of the country. Each year, most of mumps cases occurred between April and July, but a small peak also occurred in November and December. Mumps cases primarily affected the under 15 year old age group. Virologic data demonstrated that genotype F was the predominant circulating genotype throughout China for at least 15 years and no other genotype was detected between 1995 and 2010. Analysis of sequence data from the small hydrophobic (SH) gene indicated that multiple transmission chains of genotype F were found in various provinces of China, with no apparent chronologic and geographic restriction. This is the first report describing the epidemiology of mumps and genetic characterization of mumps viruses at the national level in China.

Genetic characterization of the hemagglutinin genes of wild-type measles virus circulating in china, 1993-2009.

BACKGROUND: China experienced several large measles outbreaks in the past two decades, and a series of enhanced control measures were implemented to achieve the goal of measles elimination. Molecular epidemiologic surveillance of wild-type measles viruses (MeV) provides valuable information about the viral transmission patterns. Since 1993, virologic surveillnace has confirmed that a single endemic genotype H1 viruses have been predominantly circulating in China. A component of molecular surveillance is to monitor the genetic characteristics of the hemagglutinin (H) gene of MeV, the major target for virus neutralizing antibodies. PRINCIPAL FINDINGS: Analysis of the sequences of the complete H gene from 56 representative wild-type MeV strains circulating in China during 1993-2009 showed that the H gene sequences were clustered into 2 groups, cluster 1 and cluster 2. Cluster1 strains were the most frequently detected cluster and had a widespread distribution in China after 2000. The predicted amino acid sequences of the H protein were relatively conserved at most of the functionally significant amino acid positions. However, most of the genotype H1 cluster1 viruses had an amino acid substitution (Ser240Asn), which removed a predicted N-linked glycosylation site. In addition, the substitution of Pro397Leu in the hemagglutinin noose epitope (HNE) was identified in 23 of 56 strains. The evolutionary rate of the H gene of the genotype H1 viruses was estimated to be approximately 0.76×10(-3) substitutions per site per year, and the ratio of dN to dS (dN/dS) was <1 indicating the absence of selective pressure. CONCLUSIONS: Although H genes of the genotype H1 strains were conserved and not subjected to selective pressure, several amino acid substitutions were observed in functionally important positions. Therefore the antigenic and genetic properties of H genes of wild-type MeVs should be monitored as part of routine molecular surveillance for measles in China.

Molecular epidemiology of measles viruses in China, 1995-2003.

This report describes the genetic characterization of 297 wild-type measles viruses that were isolated in 24 provinces of China between 1995 and 2003. Phylogenetic analysis of the N gene sequences showed that all of the isolates belonged to genotype H1 except 3 isolates, which were genotype A. The nucleotide sequence and predicted amino acid homologies of the 294-genotype H1 strains were 94.7%-100% and 93.3%-100%, respectively. The genotype H1 isolates were divided into 2 clusters, which differed by approximately 2.9% at the nucleotide level. Viruses from both clusters were distributed throughout China with no apparent geographic restriction and multiple co-circulating lineages were present in many provinces. Even though other measles genotypes have been detected in countries that border China, this report shows that genotype H1 is widely distributed throughout the country and that China has a single, endemic genotype. This important baseline data will help to monitor the progress of measles control in China.

[Study on a high coverage of measles vaccine while high incidence of measles disease still appeared in Shaanxi province].

OBJECTIVE: To analyze the affecting factors on the cause of measles and measles vaccine under the high coverage of measles vaccine in Shaanxi province. METHODS: Age distribution and vaccination history on measles cases were studied. Throat swabs were obtained from measles cases. Measles virus was isolated from collected specimens with phenol-chloroform extraction method. Amplification was performed by RT-PCR in order to amplify 450 bp fragment of the -COOH side of N gene,and then the sequences of PCR products were detected to confirm the gene type of measles virus. Sera were obtained from patients who were in acute phase of measles disease,and antibody titer against measles vaccine strain and wild strain were determined by small amounts neutralization test. RESULTS: Measles cases with the history of measles vaccination were accounted for 38.97% of the total numbers. The geometrical mean titer (GMT) (56.18) against S191 attenuated strain was significant higher than that of wild strain (26.90) among these measles patients with history of having received measles vaccination. The GMT (25.40) against S191 attenuated strain was similar to that of wild strain (27.86) among these measles patients with non-history of measles vaccination. The antibody negative rate against wild strain was 19.15% to these sera from patients with the history of measles vaccination and antibody potency against S191 strain was less than 16. CONCLUSION: The appearance of higher measles incidence under the higher coverage of measles vaccine indicated that measles epidemic strain might degenerate as the result regarding the failure of the present measles vaccine in protecting the transmission of H1 wild strain.