Bite-sized knowledge for the hungrily curious

How do viruses jump from animals to humans?

The recent coronavirus outbreak from China is believed to have originated from a wildlife market in the City of Wuhan. At the time of writing this post, it is believed that the source of the virus may have been a snake.

Previous outbreaks of other coronaviruses, SARS and MERS are believed to have jumped from civet cats and camels respectively, and other viruses like Ebola have animal origins.

So that tells us what happened, but we want to know how. To explore that, first, we need to understand how viruses work.

Viruses are a type of organic parasite infecting nearly all forms of life. To survive and reproduce, they must move through three stages: contact with a susceptible host, infection and replication, and transmission to other individuals.

Ben Longdon: How do viruses jump from animals to humans? | TED Talk

In Ben Longdon’s TED Talk, cited above, he explains that “Human viruses are covered in proteins adapted to bind with matching receptors on human respiratory cells.” Once bound, the virus hijacks the cell’s genetic material to replicate and infect other cells.

The key point in the paragraph above that the proteins around a virus are adapted to the target host. How does this happen? The key to this is rapid mutation.

… becaue viruses rapidly reproduce by the millions, the can quickly develop random mutations. Most mutations have no effect or even prove detrimental; but a small proportion may enable the pathogen to better infect a new species.

Ben Longdon: How do viruses jump from animals to humans? | TED Talk

The success of a mutated virus is dependent both on how well it is adapted to the new host, and how well it evades the host’s immune response.

Viruses are more likely to jump between hosts that are genetically similar that those that are not. In the case of SARS and MERS, the virus is believed to have jumped to humans from other warm-blooded mammals.

Coronavirus: CDC/Dr. Fred Murphy

In the case of the new coronavirus from Wuhan (scientific name “2019 Novel Coronavirus or “2019-nCoV”), if it jumped from a snake, this would seem to be between two less-similar species.

What is a coronavirus?

Coronaviruses are common in different species of animals, including camels and bats. Most of these viruses affect animals, but not people – with a few notable exceptions, as noted above.

Coronaviruses are so named because they have a halo, or crown-like appearance when viewed under an electron microscope.

Check Out Ben Longdon’s TED Talk

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