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Mumps virus

What is mumps virus?

In the prevaccination era, mumps was a common childhood disease caused by mumps virus. Its clinical symptoms include high temperature, headache, fatigue and parotitis. Although mumps is relatively benign illness, serious complications may occur. Aseptic meningitis develops in approx. 15% of cases, encephalitis in 0.02-0.03% and oorchitis in 20-30% of cases of postpubertal males. Mumps can be prevented by vaccination with live attenuated vaccines. The first vaccines were developed in 1960s, and today over 10 vaccine strains are commercially available. Most commonly used mumps vaccine strains are Jeryl Lynn, Urabe AM9, Leningrad-3 (L-3), L-Zagreb and RIT4385. It is considered that mumps is a monotypic virus and that all vaccine strains give long-lasting protection against all wild type strains. Still, mumps epidemics do occur even in highly vaccinated populations and in some cases neutralization antibodies do not offer a protection against reinfection with a wild type mumps virus belonging to a different genotype.

Mumps virus is a paramyxovirus

Based on nucleocapsid morphology, genome organization and biological properties of mumps proteins, mumps virus belongs to family Paramyxoviridae. Viruses belonging to this family have been isolated form large number of species, indicating their high genetic variability. These widely distributed pathogens are among the commonest etiological agents of respiratory infections, causing high morbidity in mortality worldwide. Among viruses belonging to this family are respiratory syncytial virus, measles virus, parainfluenza viruses, metapneumovirus and two newly emerging viruses, Nipah and Hendra.

Mumps virus biology

Mumps genome is single stranded, non-segmented negative RNA (-RNA), 15384 nucleotides long. Virions are composed of lipoprotein envelope with 3 glycoproteins: hemagglutinin-neuraminidase (HN), fusion protein (F) and small hydrophobic protein (SH). Below the inner envelope surface, there is matrix protein (M). Within the virion, there is a helical nucleocapsid (viral RNA in complex with nucleoprotein (NP)) to which phosphoprotein (P) and large protein (L) are attached. L protein is RNA-dependent RNA-polymerase.

In biology of all RNA viruses, the key feature is their high potential for continuous adaptation and evolution. Due to highly erroneous nature of RNA-dependent RNA-polymerase and large population sizes, RNA viruses possess high level of genetic diversity. Mutations can greatly influence viral biological properties and lead to existence of new strains.