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