New viruses are created through a combination of viral replication and genetic mutation. To create new virions (viral particles), viral genes are expressed to produce proteins that become part of the virion, and the viral genome (DNA or RNA) is copied through replication. The type of genome determines the replication strategy.
Mechanisms of New Virus Creation
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Viral Replication: The fundamental process involves the virus infecting a host cell, hijacking its machinery to produce multiple copies of its genetic material and proteins, and assembling new virus particles. This process is described by the provided reference: "To create new virions, the proteins that will be incorporated into the virion are made through expression of viral genes, and the virus genome is copied through the process of replication."
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Genetic Mutation: Viruses, particularly RNA viruses, have high mutation rates. Errors during replication lead to changes in their genetic code. These mutations can cause minor variations or create entirely new strains with altered characteristics, including infectivity, virulence, and drug resistance. As noted in the references, "New viruses can also emerge through genetic mutations within the virus genome, which are more common among viruses that, instead of DNA, store…", and "...viruses' genome segments can combine to make a new strain of influenza virus."
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Genetic Recombination: When a cell is infected by multiple viruses simultaneously, their genetic material can mix and match. This recombination results in novel viral genomes with unique traits. An example from the references: "Pigs can harbor human influenza and serve, as Quammen put it, as a place for viral genes to "mix and match." If that mixing causes a mutation…."
Examples of New Virus Formation
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Influenza: The flu virus is a prime example. Annual influenza vaccines are needed because the virus frequently mutates, creating new strains. The references highlight this: "of influenza every year, and why you can get a cold more than once. Q How are strains created? A Viruses have genes that carry instructions for making new…."
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Coronaviruses: The emergence of new coronaviruses, like SARS-CoV-2, illustrates how mutations and recombination can generate novel viruses with pandemic potential.
