加拿大科学家认为COVID19从动物传染到人发生在2013年

soric
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http://www.firstpost.com/health/covid-19-origin-university-of-calgary-research-shows-sars-cov-2-may-have-been-evolving-slowly-since-2013-8529141.html

COVID-19 origin: University of Calgary research shows SARS-CoV-2 may have
been evolving slowly since 2013
Scientists at the University of Calgary in Canada say that the novel
coronavirus (SARS-CoV-2) may have been circulating amongst humans since at
least 2013, though not the same variant that is responsible for the COVID-19 pandemic

COVID-19 showed up late in 2019. Since the virus is new to humans, there has been a lot of speculation about how it came to be.

While scientists have been studying the viral genome to find out more about it, it has been suggested that the virus jumped from an animal into humans. There have also been theories about it being made in a lab even though
studies point towards its origin being natural and not man-made. Last month, the World Health Assembly passed a resolution to look into the origins of
the virus.

Now, a group of scientists at the University of Calgary, Canada, say that
the COVID-19 causing virus (SARS-CoV-2) may have been circulating amongst
the human population since at least 2013, though not the same variant that
is responsible for the current pandemic.

The findings of the study are currently available in the preprint server
Biorxiv and the study hasn’t been peer-reviewed yet.

The paper also looks into the possible origins of SARS-CoV-2 and how much of a role ACE-2 receptors play in the infectivity (ability to infect) of the
virus.

A story of evolution

To be able to survive, viruses keep on evolving with their host organism. A new viral pathogen usually emerges when a virus jumps hosts — from animals to human for example. So, even if the virus was causing mild or no disease
in the original animal host, it could be highly infectious/virulent in
humans. In the case of coronaviruses, it has been found that the viruses
live inside bats without causing much damage because the immune system of
bats has evolved to keep the virus in check. But the same is not the case
with humans. As a result, we are susceptible to falling sick.

The study

The study examines the current variant of the spike protein of SARS-CoV-2
and how strongly it binds to the ACE-2 receptor in humans (hACE-2). The
binding between the spike protein of the novel coronavirus and the ACE-2
receptors on body cells is what helps the virus enter into healthy cells.

For the study, the researchers at the University of Calgary looked into
about 479 genome sequences of the novel coronavirus collected between 30
December, 2019, and 20 March, 2020, to understand its phylogeny — meaning
the evolutionary development of the virus and relation to other closely
related viruses.

Out of all the genomes, the researchers found about 16 variants of the virus and about 11 missense mutations (where a single nucleotide change makes the DNA/RNA to code for a different protein) in more than 5 percent infections, each making their own phylogenetic tree.

Another one of their initial findings was the similarities with the bat and pangolin coronavirus. The genome of SARS-CoV-2 has been found to have at
least 96% similarity to a bat coronavirus — RaTG13 — and about 90% to a
pangolin coronavirus (Pangolin-CoV). It was previously suggested that the
current virus is a combination of both these viruses that got created due to a co-infection in a host.

To study the origins, the researchers tried to create the ancestral sequence of the receptor-binding domain of the spike protein of SARS-CoV-2. Receptor binding domain is the part of the spike protein that actually identifies
and binds with the ACE-2 receptors. They created a common ancestral RBD
sequence for all SARS-COV-2 viruses and labelled it N1 and its common
ancestor with the closest animal virus — labelled N0 (N-Zero).

Here is what they discovered:

The N1 sequence was the same as that of the reference sequence from the SARS-CoV-2 virus, as expected, while the N0 sequence was unique, pointing to the unique origin of the virus.
The two RNA/DNA sequences only differ at four positions.
The ancestral sequence gave rise to various descendants and the RaTG13 is
one of the the closest relatives of the SARS-COV-2 virus. Since the RaTG13
was found around 2013, the original ancestor of the COVID-19 causing virus
must have been around at that time as well.
Interestingly, the earlier variants of the virus bound much more strongly to hACE2 than the recent one.
Conclusion

The study suggested that the binding affinity of SARS-CoV-2 may not be a
determinant of its infectivity. There must have been some other changes that caused the viral infectivity to increase in humans. Also, it is possible
that the ancestor of the virus could have been infecting humans for a while but with fewer symptoms.

★ 发自iPhone App: ChinaWeb 1.1.5

beijingren3


【 在 soric (soric) 的大作中提到: 】
: http://www.firstpost.com/health/covid-19-origin-university-of-calgary-research-shows-sars-cov-2-may-have-been-evolving-slowly-since-2013-8529141.html
: COVID-19 origin: University of Calgary research shows SARS-CoV-2 may have : been evolving slowly since 2013
: Scientists at the University of Calgary in Canada say that the novel
: coronavirus (SARS-CoV-2) may have been circulating amongst humans since at
: least 2013, though not the same variant that is responsible for the COVID-19
: pandemic
: COVID-19 showed up late in 2019. Since the virus is new to humans, there
has
: been a lot of speculation about how it came to be.
: While scientists have been studying the viral genome to find out more
about
: ...................

soric

说的还是石正丽交给北卡的RaTG13

【 在 soric (soric) 的大作中提到: 】
: http://www.firstpost.com/health/covid-19-origin-university-of-calgary-research-shows-sars-cov-2-may-have-been-evolving-slowly-since-2013-8529141.html
: COVID-19 origin: University of Calgary research shows SARS-CoV-2 may have : been evolving slowly since 2013
: Scientists at the University of Calgary in Canada say that the novel
: coronavirus (SARS-CoV-2) may have been circulating amongst humans since at
: least 2013, though not the same variant that is responsible for the COVID-19
: pandemic
: COVID-19 showed up late in 2019. Since the virus is new to humans, there
has
: been a lot of speculation about how it came to be.
: While scientists have been studying the viral genome to find out more
about
: ...................

Seventy6


武汉物理所所长说这个病毒已经不存在,不应该是交给北卡的那个,如果是给北卡的病毒,不可能等到 2020 年一月份才到美国的基因库登记。

【 在 soric (soric) 的大作中提到: 】
: 说的还是石正丽交给北卡的RaTG13
: 19
: has
: about

g
gambitny

新冠源头还是应该在广东,新冠A型的祖先就是四个广东人。2017年广东就发生过蝙蝠
冠状病毒造成的猪瘟。广东还有穿山甲病毒。还要好好查查华南农学院,这些病毒背后都有华南农学院的影子。
PCCC

这个主意好,反正中国这么多的学校,一个一个排过去,估计一百年都查不完。
【 在 gambitny (gambitnyc) 的大作中提到: 】
: 新冠源头还是应该在广东,新冠A型的祖先就是四个广东人。2017年广东就发生过蝙蝠
: 冠状病毒造成的猪瘟。广东还有穿山甲病毒。还要好好查查华南农学院,这些病毒背后
: 都有华南农学院的影子。