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  • Stated Clearly is funded by our viewers on patreon.com/statedclearly

  • Stated Clearly presents: Where do new viruses come from? If you've been

  • watching the news you've probably heard of the novel or new coronavirus which,

  • starting in late 2019, began making people ill in China. International air

  • travel has since allowed it to spread person-to-person to new countries. As

  • government's begin to issue travel restrictions and even quarantines

  • speculations about the origin of the virus began to spread online. Some claim

  • that the virus might be a genetically modified weapon but extraordinary claims

  • require extraordinary evidence. This claim currently seems highly

  • unlikely. Others suggest that the virus may be an escaped lab specimen. This

  • actually is possible, viruses have escaped from research labs in the past,

  • but as of the time that I'm recording this voice-over, investigations into this

  • idea have not yet reached any solid conclusions. Could there be another more

  • natural explanation for the origin of the virus? The answer is yes CPVOD-19

  • the new human-infecting coronavirus, may have simply evolved from an older animal-infecting

  • coronavirus. To understand how this may have happened let's first take

  • a look at viruses in general. What are viruses? Of the many things that can make

  • you sick by infecting and reproducing inside you, viruses are among the

  • smallest. If we resize this drawing to a more realistic scale you see that

  • hundreds of viruses can fit inside a single bacterial cell. That's how tiny

  • they are. Thousands of different viral species have been studied and described

  • by scientists so far, millions more likely exist. They come in many forms but

  • all species consists of a small collection of genes (stretches of either

  • DNA or RNA that carry information for making more copies of the virus) and

  • those genes are enclosed in a protective coating of protein and sometimes a lipid

  • membrane. All known viruses are parasitic but most are

  • not parasitic to humans. Instead some only target plant cells others only

  • infect bacteria and so on. A virus reproduces by getting its genes into a

  • living cell. Different viruses do this in different ways but once inside, the cell

  • acts as if the viral genes were its own genes. It begins reading them and

  • building copies of the virus instead of performing its normal tasks. Coronaviruses

  • are a huge family of virus species that infect animal cells. Some

  • infect chickens, others infect pigs, some infect humans but most of them are

  • extremely mild. They simply give you the common cold. "Corona" means crown and

  • refers to the unusually large crown like spikes sticking out of their membranes.

  • These protein spikes are selectively sticky, sort of like velcro.

  • They don't attach to most objects but are extremely sticky when they bump into

  • specific molecules found on the outsides of animal cells. Once held firmly in

  • place, the corona virus waits until swallowed by the cell. It then begins to

  • reproduce at the cells expense. Different animal species have different types of

  • molecules on the outsides of their cells. Because of this, bird infecting corona

  • viruses usually can't infect humans, their "Velcro" doesn't hold strong enough

  • to our cells. Unfortunately the natural process of

  • evolution can sometimes help a virus overcome this problem. When virus genes

  • are being copied during reproduction, mutations can occur. These are either due

  • to simple copying errors, or processes called reassortment and recombination.

  • These happen when two or more viruses infect a single cell. In most cases

  • mutations that change the shape of viral spikes render the virus useless. There

  • velcro no longer sticks to any host cells. On rare occasions, however, a chance

  • mutation will just happen to allow a virus to attach to a new host species. If

  • the modified virus is then lucky enough to encounter that new host species,

  • infection can occur. We call this a "spillover infection". The virus has

  • spilled over into a new type of host. Early on during a spillover event the

  • virus usually isn't very good at infecting its new host. It's velcro is

  • not a perfect match and many other challenges might slow the virus down.

  • Oftentimes the mutations that let it infect the new host also make it worse

  • at infecting its original host. Because of this, many spillover viruses go

  • extinct after infecting just one or two people,

  • they're usually dead ends. That said if the virus can survive and reproduce just

  • long enough, natural selection will promote any new mutations that help it

  • better spread and reproduce in the new host population. Positive mutations

  • accumulate over multiple generations, negative mutations are discarded until...

  • BAM! A new epidemic is being screamed about on the news. Though it may seem to

  • us that these new viruses just sort of pop into existence overnight, scientists

  • now know there is a long slow burn before each explosion. Genetic evidence

  • tells us that slowly evolving spill overs have been the cause of almost

  • every major outbreak known in history. In the early 2000s, a coronavirus that used

  • to only infect bats, appears to have spilled over into civets. There it

  • mutated even further and spilled over into humans. We called it the SARS virus

  • because it causes Severe Acute Respiratory Syndrome. It spread

  • internationally from person to person and several scientists were infected in

  • the lab. By the time the virus was contained, over 8,000 people had been

  • infected, over 700 died. A coronavirus from camels also recently spilled over

  • to humans causing even more deaths. Coronaviruses are not the only types of

  • animal viruses that can adapt to new hosts. HIV spilled over from chimps, most

  • likely when someone cut themselves while preparing chimp meat for dinner.

  • The swine flu came partly from pigs but we think it actually

  • evolved through a recombination with a pig virus and a bird virus. The 1918

  • Spanish flu, the big one that devastated populations all around the world, may

  • have spilled over from chickens! While the evidence is not yet conclusive, the new

  • coronavirus might just be one more example of normal evolution. A very

  • similar virus has been found in bats and another was recently discovered in

  • pangolins. These animals are endangered, they're protected, but they're often used

  • illegally for food, rituals, and alternative medicine in the region where

  • COVID-19 first broke out. Now, there are serious people checking to make sure

  • that the virus did not come from a lab, either by accident or on purpose. After all,

  • the technology to genetically modified viruses really does exist, but

  • it's important to understand that the normal process of descent with

  • modification acted upon by natural selection really does produce new

  • viruses. It happens naturally. The chance of a virus evolving to successfully

  • infect a new species is extremely low but there are over seven and a half

  • billion people on this planet, most of us interact with animals on a

  • daily basis. We keep them as pets, we eat them as food. This means that as unlikely

  • as spillover infections might be, there are billions of opportunities for one to

  • take hold every single day. Add this the fact that the entire world is now

  • connected through international flights, and you realize that what happens in

  • Vegas doesn't actually stay in Vegas, at least not the way that it used to.

  • Luckily we have international groups like the World Health Organization and

  • various centers for Disease Control to help contain outbreaks when they happen.

  • With international cooperation we have prevented many catastrophes in the past

  • and we will prevent many more in the future so long as our species continues

  • to work together. So in summary, where do new viruses come from?

  • In most cases, new viruses evolve from old viruses. Stopping the spread of

  • new viruses requires international cooperation. For up-to-date, accurate

  • information on the risks, visit the World Health Organization website at WHO.INT

  • I am Jon Perry and that is the novel coronavirus, Stated Clearly.

  • This episode of Stated Clearly was funded by our viewers on patreon.com/statedclearly

  • If you found this video helpful please do

  • consider contributing there as well. Aside from helping me out you will also

  • get secret access to a Stated Clearly animation that is no longer public. It's

  • actually the first one that I ever made and... well... you'll see. To learn more about

  • evolution and to find free tools for use in the classroom if you happen to be a

  • teacher - high school, middle school, college - visit our website at

  • stateclearly.com So long for now, stay curious!

  • you

Stated Clearly is funded by our viewers on patreon.com/statedclearly

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