Abstract
With the implementation of mumps virus (MuV) vaccination in the expanded program on immunization (EPI) in mainland China since 2008, the incidence of mumps has decreased, and the natural epidemic pattern of mumps has slightly changed during 2013–2015. The two epidemic peaks (April-July and November-December) became less obvious than those observed from 2004 to 2012. Children and adolescents younger than 15, particularly in the five-to-nine-year-old age group, remain the target group and should be the focus of high-quality immunization activities in mainland China. However, it was also found that the incidence and reported cases of mumps decreased in each age group during 2013–2015, particularly in the five-to-nine-year-old and ten-to-fourteen-year-old age groups. The proportion of mumps cases among adults in some provinces also increased. Unlike the changes in the epidemiological characteristics of mumps affected by vaccination, the data of MuV virology surveillance indicated that most of the MuV transmission chains have not yet been effectively interrupted, and MuV remains a natural epidemic pattern in mainland China. In the MuV virology surveillance, 194 MuV strains during 2013–2015 were isolated from 10 of 31 provinces in mainland China. Based on the phylogenetic analysis of the small hydrophobic (SH) gene, both genotype F (99.0%) and G (1.0%) were identified, and genotype F was still the predominant genotype continuously circulating in mainland China. Representative genotype F and G strains isolated in China from 1995 to 2012 were selected for further analysis. The results indicated that there were multiple transmission chains within genotype F, with no obvious geographical or time differences. The high genetic diversity of genotype F strains could be a result of the continuous transmission and evolution of the MuV in mainland China. Genotype G was also detected in four provinces in mainland China. Because of the limited epidemiological data, it was uncertain whether the genotype G MuV strains found in 2011 and 2013 were imported from other countries. Therefore, combined high-quality epidemiological and virological surveillance is necessary for mumps control; it can also be used to observe the changes in epidemiological characteristics and viral transmission of mumps over time after mumps-containing vaccine (MuCV) implementation and to provide a comprehensive epidemiological and genetic baseline for mumps elimination in mainland China.
Highlights
Mumps is caused by the mumps virus (MuV) and is a type of acute respiratory infectious diseases that is prevalent worldwide
In 2015, mumps incidence had declined by 62.29% compared to 2012 and the incidence had declined by 36.64% compared to the average incidence from 2004 to 2010 (21.18/ 100,000) (Fig 1A)
There were obvious seasonal patterns, which are a well-known and described feature of mumps, and most of the mumps cases were concentrated between April and July, with small peaks occurring in November and December in mainland China
Summary
Mumps is caused by the mumps virus (MuV) and is a type of acute respiratory infectious diseases that is prevalent worldwide. The MuV genome is a non-segmented single-stranded negative strand RNA that contains 15,384 nucleotides. It encodes seven tandemly linked transcription units: the nucleo-(N), V/phosphor-/I (V/ P/I), matrix (M), fusion (F), small hydrophobic (SH), hemagglutinin-neuraminidase (HN), and large (L) proteins [1,2]. MuV has been shown to have 12 genotypes (A-N, excluding E and M) circulating in the world [3], among which there is large diversity. In mainland China, genotype F has been the predominant MuV genotype, and it was the native prevailing MuV genotype during 1995–2010 in mainland China [4]
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