Mumps virus F gene and HN gene sequencing as a molecular tool to study mumps virus transmission

• We analyzed mumps virus sequences from 109 cases (2004–2015) in the Netherlands.
• Nucleotide diversity increased when F and H genes were added to the analysis.
• Transmission chains can be identified during a mumps genotype G outbreak season.
• The genetic diversity indicates multiple mumps introductions in the Netherlands.

Various mumps outbreaks have occurred in the Netherlands since 2004, particularly among persons who had received 2 doses of measles, mumps, and rubella (MMR) vaccination. Genomic typing of pathogens can be used to track outbreaks, but the established genotyping of mumps virus based on the small hydrophobic (SH) gene sequences did not provide sufficient resolution. Therefore, we expanded the sequencing to include fusion (F) gene and haemagglutinin-neuraminidase (HN) gene sequences in addition to the SH gene sequences from 109 mumps virus genotype G strains obtained between 2004 and mid 2015 in the Netherlands. When the molecular information from these 3 genes was combined, we were able to identify separate mumps virus clusters and track mumps virus transmission. The analyses suggested that multiple mumps virus introductions occurred in the Netherlands between 2004 and 2015 resulting in several mumps outbreaks throughout this period, whereas during some local outbreaks the molecular data pointed towards endemic circulation. Combined analysis of epidemiological data and sequence data collected in 2015 showed good support for the phylogenetic clustering.