New viruses can also emerge through genetic mutations within the virus genome, which are more common among viruses that, instead of DNA, store their genetic information in the similar molecule RNA. There is also genetic evidence that this mechanism can occur in coronaviruses, although its role in the emergence of SARS-CoV-2 remains to be determined. This is what we think happened with the 2009 H1N1 influenza epidemic, with the shift occurring in pigs and then jumping to humans to start the outbreak. This shift in the influenza virus is called antigenic shift. If the proteins on the surface of the new virus have significantly changed from currently circulating influenza virus strains, then no one will have immunity and the new virus can easily spread. The virus contains eight genome segments and if two different viruses infect the same cell, segments from both can mix to create a novel virus species. Chameleons Eye/Shutterstockįrom research over the past few decades, we understand some of the mechanisms that contribute to virus jumps between species. Or the virus may simply be unable to replicate inside the cell for whatever reason.īird flu can cross over to humans so requires protective measures. When attacking a cell, a virus binds to specific receptor molecules on the cell’s surface and so may not be able to bind to other types of cell. This is not a given, as many viruses can only infect specific types of cells, such as lung cells or kidney cells. In order for a virus to successfully jump into a new species of host it must be able to do several things.įirst, it must be able to establish an infection in the new host by replicating itself there. The first thing to know is that it is rare for viruses to jump between species. So how do new viruses actually emerge from the environment and start infecting humans? Every virus has a unique origin in terms of its timing and mechanism, but there are some general facts that are true for all species of emerging virus. Bats have been identified as the animal with the closest known equivalent virus although, again, we’re not sure that a bat provided the direct origin of SARS-CoV-2.
The virus in question, known as SARS-CoV-2, has been linked to a “wet market” for wild animal trade in Wuhan, China, although it’s by no means certain this was the source of the human version of the virus. The recent emergence of the novel coronavirus behind the COVID-19 pandemic has thrown a spotlight on the risks that animals can pose to humans as the source of new viruses.
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