The WHO recently proposed an updated nomenclature for mumps virus (MuV). WHO currently recognizes 12 genotypes of MuV, assigned letters from A to N (excluding E and M), which are based on the nucleotide sequences of small hydrophobic (SH) and haemagglutinin-neuraminidase (HN) genes. A total of 66 MuV genomes are available in GenBank, representing eight of the 12 genotypes. To complete this dataset, whole genomes of seven isolates representing six genotypes (D, H, I, J, K and L) and one unclassified strain were sequenced. SH and HN genes of other representative strains were also sequenced. The degree of genetic divergence, predicted amino acid substitutions in the HN and fusion (F) proteins and geographic distributions of MuV strains were analysed based on the updated dataset. Nucleotide heterogeneity between genotypes reached 20% within the SH gene, with a maximum of 9% within the HN gene. The geographic and chronologic distributions of the 12 genotypes were summarised. This review contributes to our understanding of strain diversity for wild type MuV, and the results support the current WHO nomenclature.

A recent resurgence of mumps in doubly vaccinated cohorts has been observed, identifying genotype G as the current predominant genotype. In this study, the neutralization efficacy of guinea pig sera immunized with three vaccine viruses: L-Zagreb, Urabe AM9 and JL5, was tested against seven mumps viruses: three vaccine strains and four wild-type strains (two of genotype G, one of genotype C, one of genotype D) isolated during 1998-2011. All sera neutralized all viruses although at different levels. The neutralization efficiency of sera decreases several fold by temporal order of virus isolation. Therefore, we concluded that gradual evolution of mumps viruses, rather than belonging to a certain genotype, results in an antigenic divergence from the vaccine strains that decrease the neutralization capacity of vaccine-induced antibodies. Moreover, the amino-acid sequence alignment revealed three new potentially relevant regions for escape from neutralization, i.e. 113-130, 375-403 and 440-443.

The HPIV3 subclaster C3 (genetic lineage C3a) became the most detected circulating HPIV3 strain in Croatia. The results indicated that the HN 582 nt and the entire F gene sequences were as good for phylogenetic analysis as the entire HN gene sequence.

Human metapneumovirus (HMPV) is recognized as a global and frequent cause of acute respiratory tract infections among people of all ages. The objectives of this study were molecular epidemiology and evolutionary analysis of HMPV strains which produced moderate and severe acute respiratory tract infections in children in Croatia during four consecutive seasons (2011-2014). A total of 117 HMPV-positive samples collected from hospitalized pediatric patients presenting with acute respiratory tract infections and tested by direct immunofluorescence assay were first analyzed by amplifying a part of the F gene. Sixteen samples were further analyzed based on complete F, G, and SH gene sequences. HMPV genome was identified in 92 of 117 samples (78%) and the circulation of multiple lineages of HMPV was confirmed. In 2011, 2012, and 2014, subgroups A2 and B2 co-circulated, while B1 gained prevalence in 2013 and 2014. The study established the presence of a novel subcluster A2c in Croatia. This subcluster has only recently been detected in East and Southeast Asia. This study provides new insights into epidemiology and genetic diversity of HMPV in this part of Europe.

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