Paramyxoviridae (from Greek para- “by the side of” and myxa “mucus”) is a family of negative-strand RNA viruses in the order Mononegavirales. Vertebrates serve as natural hosts. Diseases associated with this family include measles, mumps, and respiratory tract infections. The family has nine subfamilies that contain 23 genera.

Structure

Virions are enveloped and can be spherical or pleomorphic and capable of producing filamentous virions. The diameter is around 150 nm. Genomes are linear, around 15kb in length. Fusion proteins and attachment proteins appear as spikes on the virion surface. Matrix proteins inside the envelope stabilise virus structure. The nucleocapsid core is composed of the genomic RNA, nucleocapsid proteins, phosphoproteins and polymerase proteins. Translation takes place by leaky scanning, ribosomal shunting, and RNA termination-reinitiation. The virus exits the host cell by budding. Vertebrates, including humans and birds serve as the natural hosts. Transmission route is airborne particles.

Taxonomy

thumb|Phylogenetic tree of paramyxoviruses|alt=

The family contains the following subfamilies and genera (-virinae denotes subfamily and -virus denotes genus):

The human parainfluenza viruses (HPIV) are the second most common causes of respiratory tract disease in infants and children. There are four types of HPIVs, known as HPIV-1, HPIV-2, HPIV-3 and HPIV-4. HPIV-1 and HPIV-2 may cause cold-like symptoms, along with croup in children. HPIV-3 is associated with bronchiolitis, bronchitis, and pneumonia. HPIV-4 is less common than the other types, and is known to cause mild to severe respiratory tract illnesses.

Paramyxoviruses are also responsible for a range of diseases in other animal species, for example canine distemper virus (dogs), phocine distemper virus (seals), cetacean morbillivirus (dolphins and porpoises), Newcastle disease virus (birds), and rinderpest virus (cattle).

Some paramyxoviruses, such as the henipaviruses, are zoonotic pathogens, occurring naturally in an animal host, but also able to infect humans. Hendra virus and Nipah virus in the genus Henipavirus have emerged in humans and livestock in Australia and Southeast Asia. Both viruses are contagious, highly virulent, and capable of infecting a number of mammalian species and causing potentially fatal disease. Due to the lack of either a licensed human vaccine (a Hendra virus vaccine exists for horses) or antiviral therapies, Hendra virus and Nipah virus are designated as Biosafety level (BSL) 4 agents. The genomic structure of both viruses is that of a typical paramyxovirus.

Diversity and evolution

Novel paramyxoviruses have been discovered in both terrestrial and aquatic animals, demonstrating a vast host range and great viral genetic diversity. As molecular technology advances and viral surveillance programs are implemented, the discovery of new viruses in this group is increasing. Within the second clade the respiroviruses appear to be the basal group. The respirovirus-henipavirus-morbillivirus clade may be basal to the avulavirus-rubulavirus clade.

See also

  • Animal virology
  • Virology

References

  • ICTV Report: Paramyxoviridae
  • Paramyxoviruses (1998) — morphology, genome, replication, pathogenesis (special access required)
  • Animal viruses
  • Paramyxoviridae Genomes Viral Bioinformatics Resource Center
  • Viralzone: Paramyxoviridae
  • Virus Pathogen Database and Analysis Resource (ViPR): Paramyxoviridae 2022 archive