Viral evolutionViral evolution is a subfield of evolutionary biology and virology that is specifically concerned with the evolution of viruses. Viruses have short generation times, and many—in particular RNA viruses—have relatively high mutation rates (on the order of one point mutation or more per genome per round of replication). Although most viral mutations confer no benefit and often even prove deleterious to viruses, the rapid rate of viral mutation combined with natural selection allows viruses to quickly adapt to changes in their host environment.
Rous sarcoma virusRous sarcoma virus (RSV) (raʊs) is a retrovirus and is the first oncovirus to have been described. It causes sarcoma in chickens. As with all retroviruses, it reverse transcribes its RNA genome into cDNA before integration into the host DNA. RSV was discovered in 1911 by Peyton Rous, working at Rockefeller University in New York City, by injecting cell free extract of chicken tumour into healthy Plymouth Rock chickens. The extract was found to induce oncogenesis. The tumour was found to be composed of connective tissue (a sarcoma).
Viral life cycleViruses are only able to replicate themselves by commandeering the reproductive apparatus of cells and making them reproduce the virus's genetic structure and particles instead. How viruses do this depends mainly on the type of nucleic acid DNA or RNA they contain, which is either one or the other but never both. Viruses cannot function or reproduce outside a cell, and are totally dependent on a host cell to survive. Most viruses are species specific, and related viruses typically only infect a narrow range of plants, animals, bacteria, or fungi.
Viral quasispeciesA viral quasispecies is a population structure of viruses with a large number of variant genomes (related by mutations). Quasispecies result from high mutation rates as mutants arise continually and change in relative frequency as viral replication and selection proceeds. The theory predicts that a viral quasispecies at a low but evolutionarily neutral and highly connected (that is, flat) region in the fitness landscape will outcompete a quasispecies located at a higher but narrower fitness peak in which the surrounding mutants are unfit.
Hepatitis C virusThe hepatitis C virus (HCV) is a small (55–65 nm in size), enveloped, positive-sense single-stranded RNA virus of the family Flaviviridae. The hepatitis C virus is the cause of hepatitis C and some cancers such as liver cancer (hepatocellular carcinoma, abbreviated HCC) and lymphomas in humans. The hepatitis C virus belongs to the genus Hepacivirus, a member of the family Flaviviridae. Before 2011, it was considered to be the only member of this genus. However a member of this genus has been discovered in dogs: canine hepacivirus.
Human betaherpesvirus 5Human betaherpesvirus 5, also called human cytomegalovirus (HCMV), is species of virus in the genus Cytomegalovirus, which in turn is a member of the viral family known as Herpesviridae or herpesviruses. It is also commonly called CMV. Within Herpesviridae, HCMV belongs to the Betaherpesvirinae subfamily, which also includes cytomegaloviruses from other mammals. CMV is a double-stranded DNA virus. Although they may be found throughout the body, HCMV infections are frequently associated with the salivary glands.
RitonavirRitonavir, sold under the brand name Norvir, is an antiretroviral medication used along with other medications to treat HIV/AIDS. This combination treatment is known as highly active antiretroviral therapy (HAART). Ritonavir is a protease inhibitor and is used with other protease inhibitors. It may also be used in combination with other medications to treat hepatitis C and COVID-19. It is taken by mouth. Tablets of ritonavir are not bioequivalent to capsules, as the tablets may result in higher peak plasma concentrations.
Virulent Newcastle diseaseVirulent Newcastle disease (VND), formerly exotic Newcastle disease, is a contagious viral avian disease affecting many domestic and wild bird species; it is transmissible to humans. Though it can infect humans, most cases are non-symptomatic; rarely it can cause a mild fever and influenza-like symptoms and/or conjunctivitis in humans. Its effects are most notable in domestic poultry due to their high susceptibility and the potential for severe impacts of an epizootic on the poultry industries.
Measles morbillivirusMeasles morbillivirus (MeV), also called measles virus (MV), is a single-stranded, negative-sense, enveloped, non-segmented RNA virus of the genus Morbillivirus within the family Paramyxoviridae. It is the cause of measles. Humans are the natural hosts of the virus; no animal reservoirs are known to exist. Measles The virus causes measles, a highly contagious disease transmitted by respiratory aerosols that triggers a temporary but severe immunosuppression.
Spanish fluThe 1918-20 flu pandemic, also known as the Great Influenza epidemic or by the common misnomer of the Spanish flu, was an exceptionally deadly global influenza pandemic caused by the H1N1 influenza A virus. The earliest documented case was March 1918 in the state of Kansas in the United States, with further cases recorded in France, Germany and the United Kingdom in April. Two years later, nearly a third of the global population, or an estimated 500 million people, had been infected in four successive waves.
