Molecular epidemiology of mumps viruses detected in the Netherlands, 2017-2019

Mumps cases continue to occur, also in countries with a relatively high vaccination rate. The last major outbreaks of mumps in the Netherlands were from 2009-2012 and thereafter, only small clusters and single cases were reported. Molecular epidemiology can provide insights in the circulation of mumps viruses. The aims of the present study were to analyze the molecular epidemiology of mumps viruses in the Netherlands in 2017-2019 and to elucidate whether complete genome sequencing adds to the molecular resolution of mumps viruses when compared to sequencing of the mumps SH gene and non-coding regions (SH+NCRs). To this end, Sanger sequence data from the SH+NCRs were analyzed from 82 mumps genotype G viruses. In addition, the complete genomes were obtained from 10 mumps virus isolates using next-generation sequencing. Analysis of SH+NCRs of mumps viruses revealed the presence of two major lineages in the Netherlands, which was confirmed by analysis of complete genomes. Comparison of molecular resolution obtained with SH+NCRs and complete genomes clearly indicated that additional molecular resolution can be obtained by analyzing complete genomes. In conclusion, analysis of SH + NCRs sequence data from recent mumps genotype G viruses indicate that mumps viruses continue to circulate in the Netherlands and surrounding countries. However, to understand exact transmission trees and to compare mumps viruses on a large geographic scale, analysis of complete genomes is a very useful approach.