Where Do New Viruses Come From?


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

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