
Single mutation is all that was needed to get to Covid-19 (2019) - jinnko
https://www.mdpi.com/1999-4915/11/3/210/htm
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eindiran
Changing the title of this article did it a disservice, as its no longer clear
that this was a research paper arguing the importance of studying bat-origin
coronaviruses in China from January 2019, well before SARS-CoV-2 made its
appearance. The paper also covers a theory of why bats can be long-term
carriers of coronaviruses without showing symptoms of disease:

"It is hypothesized that flight provided the selection pressure for
coexistence with viruses, while the migratory ability of bats has particular
relevance in the context of disease transmission [16]. Indeed, bats were
linked to a few highly pathogenic human diseases, supporting this hypothesis.
Some of these well characterized bat viruses, including bat lyssaviruses
(Rabies virus), henipaviruses (Nipah virus and Hendra virus), CoVs (SARS-CoV,
MERS-CoV, and SADS-CoV), and filoviruses (Marburg virus, Ebola virus, and
Mengla virus), pose a great threat to human health [16,17]. A comprehensive
analysis of mammalian host–virus relationships demonstrated that bats harbor a
significantly higher proportion of zoonotic viruses than other mammalian
orders [18]. Viruses from most of the viral families can be found in bats
[16]."

~~~
akiselev
_> The paper also covers a theory of why bats can be long-term carriers of
coronaviruses without showing symptoms of disease_

Specifically, citation 77: _Xie, J.; Li, Y.; Shen, X.; Goh, G.; Zhu, Y.; Cui,
J.; Wang, L.F.; Shi, Z.L.; Zhou, P. Dampened STING-Dependent Interferon
Activation in Bats. Cell Host Microbe 2018, 23, 297–301_

My reading is: the STING protein activates type I interferon which in turn
activate the immune system which hones in on viruses and infected cells. In
bats either the production of STING or the type I interferon response is
dampened so unless the virus is specifically harmful to bat biology, the
immune system will largely keep it in check or ignore the virus (possibly)
without causing problems with homeostasis (fever, etc) and
inflammatory/autoimmune responses.

That raises an interesting question: are bats a keystone species for many
zoonotic viruses w.r.t. human civilization? Lots of viruses like ebola and
nipah virus are too deadly or not infectious enough to spread very far outside
of metropolitan areas and most of the rest don't mutate as fast as the flu so
we can stamp them out with vaccinations and modern public health institutions.
What if bats are the species keeping those viruses alive and mutating, causing
outbreaks across species and continents?

Other studies have shown that viruses spread very fast in bats like, for
example, rabies which can be found in anywhere from 15% to 50% of the bat
population depending on the continent. This holds for many viruses that effect
many species so if they're basically immune, what if bats are in a symbiotic
evolutionary relationship with viruses? All the zoonotic viruses that don't
target bats outcompete the viruses in bats that do and "in return" the bats
immune system ignores them, shedding their viral load all over the place,
causing outbreaks even with diseases that would have naturally wiped
themselves out.

~~~
eindiran
> That raises an interesting question: are bats a keystone species for many
> zoonotic viruses w.r.t. human civilization?

I think that's a very reasonable hypothesis. Reading over the list of zoonotic
diseases listed here[0], bats and rodents seem to be the leading sources of
viruses.

[0]
[https://en.wikipedia.org/wiki/Zoonosis](https://en.wikipedia.org/wiki/Zoonosis)

