The main difference between paramyxovirus and orthomyxovirus is that paramyxovirus contains a non-segmented ssRNA genome with negative polarity, whereas orthomyxovirus contains an ssRNA genome segmented into 8 pieces of negative polarity.
Paramyxovirus and orthomyxovirus are two types of RNA viruses that primarily infect the respiratory tract. In general, paramyxovirus causes respiratory syncytial virus (RSV), measles, mumps, and parainfluenza, while the only clinical importance of orthomyxovirus is causing influenza.
Key Areas Covered
1. What is Paramyxovirus
– Definition, Structure, Function
2. What is Orthomyxovirus
– Definition, Structure, Function
3. Similarities – Paramyxovirus and Orthomyxovirus
– Outline of Common Features
4. Difference Between Paramyxovirus and Orthomyxovirus
– Comparison of Key Differences
Key Terms
Orthomyxovirus, Paramyxovirus
What is Paramyxovirus
Paramyxovirus is a single-stranded RNA virus. It is an enveloped virus that undergoes replication in the cytoplasm. Moreover, paramyxovirus causes different types of infections in vertebrates; that includes measles virus, mumps virus, parainfluenza virus, and respiratory syncytial virus (RSV) infections. Respiratory droplets are the primary method of spreading this virus. Therefore, hand-washing, proper hygiene, and vaccination are methods to avoid paramyxovirus infections.
Figure 1: Paramyxovirus
Furthermore, paramyxovirus belongs to the family Paramyxoviridae which has two subfamilies relevant to humans. They are Pneumovirinae and Paramyxovirinae. Of these, Pneumovirinae contains the genus Pneumovirus, giving rise to the respiratory syncytial virus. Meanwhile, Paramyxovirinae contains the genus Morbillivirus, causing measles virus or rubeola. The genus Respirovirus gives rise to para-influenza viruses 1 and 3a, while the genus Rubulavirus gives rise to mumps virus and para-influenza viruses 2 and 4.
What is Orthomyxovirus
Orthomyxovirus, or the influenza virus, is another RNA virus that only gives rise to the genus Orthomyxovirus, consisting of three types (species): A, B, and C. The most significant feature of orthomyxovirus is the causing of influenza, an acute respiratory disease showing prominent systemic symptoms. The influenza is an upper and lower respiratory tract infection. It is characterized by the sudden onset of fever, malaise, cough, and myalgia, while the common serious complication is pneumonia.
Figure 2: Orthomyxovirus
Moreover, the influenza virus binds to the host via hemagglutinin. Neuraminidase is the other best-characterized protein in the genome. Both are glycoproteins. Depending on the type of ribonucleoprotein, there are three species of influenza; they are influenza A, B, and C. Influenza A causes most pandemics. Meanwhile, influenza B causes most outbreaks, while influenza C is non-pandemic and causes minor infections.
Similarities Between Paramyxovirus and Orthomyxovirus
- Paramyxovirus and orthomyxovirus are two types of RNA viruses.
- They belong to the kingdom Orthornavirae and phylum Orthornavirae.
- Both contain negative sense ssRNA genomes. In addition, the genome encodes RNA-dependent RNA polymerase.
- Furthermore, both are enveloped viruses with a capsid.
Difference Between Paramyxovirus and Orthomyxovirus
Definition
Paramyxovirus refers to a type of virus that has hemagglutinin-neuraminidase proteins in the outer coat and RNA as the genetic material while orthomyxovirus refers to any of a family (Orthomyxoviridae) of single-stranded RNA viruses that have a spherical or filamentous virion.
Taxonomy
Paramyxovirus belongs to the family Paramyxoviridae, while orthomyxovirus belongs to the family Orthomyxoviridae.
Size
Moreover, paramyxovirus is larger, 150-300 nm in diameter, while orthomyxovirus is smaller, 80 to 120 nm in diameter.
Genome
The genome of the paramyxovirus is non-segmented, while the genome of the orthomyxovirus contains 8 segments.
Surface Spikes
Paramyxovirus contains hemagglutinin (H) and neuraminidase (N) in the same spikes, while orthomyxovirus contains hemagglutinin (H) and neuraminidase (N) in different spikes.
Antigenic Variation
Antigenic drift is the only type of antigenic variation in paramyxovirus, while antigenic shift and antigenic drift occur in orthomyxovirus.
Giant Cell Formation
Paramyxovirus undergoes giant cell formation that is multinucleated and occurs through fusion or division of mononuclear cells while orthomyxovirus does not undergo giant cell formation.
Diseases
Paramyxovirus causes respiratory syncytial virus (RSV) disease, measles, mumps, and parainfluenza, while the only clinical importance of orthomyxovirus is the causing of influenza.
Conclusion
In brief, paramyxovirus and orthomyxovirus are two types of RNA viruses with single-stranded RNA genomes. Paramyxovirus is a larger virus containing a non-segmented genome. It also contains hemagglutinin (H) and neuraminidase (N) in the same spikes. Meanwhile, the antigenic variation of paramyxovirus is antigenic drift. In addition, the types of diseases caused by paramyxovirus include respiratory syncytial virus (RSV) disease, measles, mumps, and parainfluenza. In comparison, orthomyxovirus is smaller and contains 8 segments in the genome. However, the hemagglutinin (H) and neuraminidase (N) surface spikes occur in different spikes in orthomyxovirus. However, the main clinical importance of orthomyxovirus is the occurrence of influenza. Therefore, the main difference between paramyxovirus and orthomyxovirus is their genome segmentation.
References:
- Park GYS, Tishkowski K. “Paramyxovirus.” In: StatPearls [Internet]. Treasure Island (FL): StatPearls Publishing; 2023 Jan-.
- “Orthomyxoviruses.” In: Baron S, editor. Medical Microbiology. 4th edition. Galveston (TX): the University of Texas Medical Branch at Galveston; 1996. Chapter 58.
Image Courtesy:
- “Paramyxoviridae-Schema” By Gleiberg – Own work (CC BY-SA 2.0 de) via Commons Wikimedia
- “Fimmu-09-01581-g001.” By Dan Dou, Rebecca Revol, Henrik Östbye, Hao Wang, and Robert Daniels – Own Work (CC BY 4.0) via Commons Wikimedia
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