Before March 2020, many people saw pandemics as a thing of the past. Then came COVID-19. Scientists still do not know exactly where the virus that caused it — SARS-CoV-2 — came from, but it soon reached almost every country worldwide. Over 2 years, the virus has evolved, producing several variants. In this Special Feature, we look at the evolution of SARS-CoV-2 and ask what lessons scientists have learned.

1. 2 years into the pandemic,
what have we learned?
Before March 2020, many people saw pandemics as a thing
of the past. Then came COVID-19. Scientists still do not
know exactly where the virus that caused it — SARS-CoV-2
— came from, but it soon reached almost every country
worldwide. Over 2 years, the virus has evolved, producing
several variants. In this Special Feature, we look at the
evolution of SARS-CoV-2 and ask what lessons scientists
have learned.

2. Shar e on Pi
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er
est
What have we learned in 2 years of COVID-19? Image credit: Dia Dipasupil/Getty Images.
In late 2019, there was a sudden increaseTrusted Source in pneumonia cases in central
China. By January 7, scientists had identified and isolated a previously unknown
coronavirus, now designated SARS-CoV-2.
On March 11, 2020, the World Health Organization (WHO)Trusted Source declared COVID-
19 a pandemic.
Now, 2 years on, authorities have recorded more than 458 million cases of COVID-19, the
disease resulting from SARS-CoV-2. The disease has also played a role in the deaths of
more than 6 million people.

3. Stay informed with live updates on the current COVID-19 outbreak and visit our coronavirus
hub for more advice on prevention and treatment.
However, the actual death toll may well be far higher than 6 million. According to a recent
paper in The LancetTrusted Source, the actual death toll may be at least three times that.
The first cases
On December 29, 2019, experts linkedTrusted Source four cases of pneumonia of
unknown etiologyTrusted Source to the Huanan Seafood Wholesale Market in Wuhan,
central China.
On January 7, 2020, researchers isolated the causative agent, SARS-CoV-2, and on
January 10, they sequenced its genome.
By January 2, 2020, doctors had confirmed that 41 peopleTrusted Source in a Wuhan
hospital with severe respiratory illness had a SARS-CoV-2 infection. Of these individuals,
27 had had exposure to the seafood market.
We have to keep our body fit and healthy to face the various viruses coming regulary in
different forms
Other human coronaviruses
Many coronaviruses exist, affecting both animals and people. Most cause infections with mild to
moderate symptoms in the upper respiratory tract, such as colds.
In recent years, two coronaviruses — SARS-CoV and MERS-CoVTrusted Source — have caused
more severe disease. SARS-CoV, which scientists identified in November 2002, was responsible for
severe acute respiratory syndrome (SARS), which emerged in Asia. The Centers for Disease Control
and Prevention (CDC)Trusted Source note that of the 8,096 people with a known SARS infection,
774 died. There have been no reported cases since 2004.
Scientists first identified Middle East Respiratory Syndrome (MERS), the disease that MERS-CoV-2
causes, in 2012 in Saudi Arabia. The mortality rate for MERS is high — of every 10 people with the
infection, three or fourTrusted Source die. There continue to be occasional, localized outbreaks of
this disease.

4. Both of these coronaviruses caused diseases with high fatality rates, but it was possible to contain the
spread before they reached pandemic levels. So, were we ready for the next coronavirus?
The origins of SARS-CoV-2
Experts believe that SARSTrusted Source came from bats and that MERSTrusted Source crossed
over to people from camels. However, for SARS-CoV-2, researchers have not all agreed on any of
the many existing theories.
At first, people thought that SARS-CoV-2 might have come directly from batsTrusted Source.
Scientists discounted that theory, though, as the spike protein on SARS-CoV-2 is very different from
that on the coronaviruses present in bats.
Now, researchers think it is likely that the virus originated in bats but had an intermediate host
between bats and people. A recent study — which has not yet undergone peer review — suggests
that live mammals for sale at the Huanan Seafood Wholesale Market in Wuhan, the epicenter of early
cases, might have been the intermediate host.
Another recent study — also yet to undergo peer review — that analyzed the evolution of SARS-
CoV-2 suggests that “SARS-CoV-2 emergence likely resulted from multiple zoonotic events.” The
researchers do not suggest what the intermediate animal hosts might be.
Alternatively, did SARS-CoV-2 escape from a laboratory in Wuhan, as some media
outletsTrusted Source have suggested? The WHOTrusted Source has dismissed this theory as
“extremely unlikely.”
So, there is still uncertainty about the origins of SARS-CoV-2. And this may be due, in some
measure, to a lack of international cooperation, as Prof. Jonathan Stoye, a virologist at the Francis
Crick Institute in London, United Kingdom, told Medical News Today.
In his opinion, “one mistake was to start pointing fingers at China and blaming them for the origin of
this virus. I think that, naturally, led to pushback from the Chinese [authorities].”
He added: “I absolutely believe in natural origins [of SARS-CoV-2], but the Chinese [authorities]
could have made things easier if they’d opened up their books straightaway. They weren’t going to
do that when they were being accused of being responsible [for the virus].”

5. The rise of variants
For almost a year, the original Wuhan variant of SARS-CoV-2 moved across the globe. Then, in late
2020, the number of COVID-19 cases increased rapidly in South East England, in the United
Kingdom.
Researchers discovered that a new variant, which was 50% more transmissibleTrusted Source than
the original and had 17 unique mutationsTrusted Source, was responsible. In December 2020, the
WHO designated it B.1.1.7, or the Alpha variant.
Scientists have since identified many other variants, but the WHO has only designated five
as variants of concern (VOC)Trusted Source. The VOCs and the location of their initial
identification areTrusted Source:
 Alpha (B.1.1.7): The U.K., September 2020
 Beta (B.1.351): South Africa, October 2020
 Gamma (P.1): Brazil, December 2020
 Delta (B.1.617.2): India, October 2020
 Omicron (B.1.1.529): Multiple countries, November 2021
Each variant has different features. Some variants are more transmissible than others, and some are
more virulent. It is these features that have caused the multiple waves of COVID-19.
“The regular and rapid emergence of new variants in the past 2 years have made the course of the
pandemic very unpredictable.”
– Dr. Arturo Casadevall, distinguished professor and chair of molecular microbiology and
immunology and infectious diseases at the Johns Hopkins Bloomberg School of Public Health in
Baltimore
What causes variants?
Viruses mutateTrusted Source all the time. Each time they replicate, which they do frequently, their
genetic material is copied. A mutation happens when part of the genetic material is copied
incorrectly.

6. In a coronavirus, the genetic material is ribonucleic acid (RNA). An enzyme called RNA polymerase
controls the replication, and it often makes errors. Most mutations create a virus that cannot replicate
and spread among people. However, some mutations lead to a virus that can replicate: a variant.
A mutation might give the virus a selective advantage, such as better transmissibility or greater
virulence. If it is more transmissible, the variant may spread faster and outcompete previous
variants. This is what happened with the Alpha, Delta, and Omicron variants of the
coronavirus.
Some situations give viruses more opportunities to mutate, as Dr. Christopher Coleman, assistant
professor of infection immunology at the University of Nottingham, U.K., explained to MNT:
“Viruses naturally mutate as they replicate, so in an immunocompromised host where the virus
replicates more easily, there will be a correspondingly increased number of mutations.”
Omicron has more than 50 mutationsTrusted Source, of which some 30Trusted Source are in the
spike protein that the virus uses to gain entry to host cells. One theory suggests that it may have
evolved in people with HIV, a virus that suppresses the immune system.
Hosts and mutations
Moving between host species also increases the mutation rate. Dr. Coleman added that the
“[i]nfection of animals by humans will mean the virus then adapts to a new host, which
involves mutations.”
Domestic animals, such as cats, dogs, and ferrets, have had SARS-CoV-2 infections.
The CDCTrusted Source notes that on one mink farm in Michigan, several animals
contracted the virus, which then passed back to workers. On testing, the viral samples from
the workers contained several mink-related mutations.
“You are getting evolution occurring from different starting points. Whether they are
occurring through immunosuppressed or immunocompromised patients, or whether they
are happening through animals, or how, I don’t know that we know, and I don’t know that we
will ever really know.”
— Prof. Jonathan Stoye

7. Vaccines
Decades of research into coronaviruses led to the rapid development of vaccines, many of
them using new technologies. These have been incredibly effectiveTrusted Source in
reducing the impact of COVID-19 and allowing society to regain some measure of
normality.
But, as Prof. Stoye explained, “[i]n retrospect, we have been ‘lucky’ that it has been
possible to make a vaccine against this particular virus, whereas for things like HIV
[…], we still don’t have vaccines.”
However, vaccines designed against one variant might be ineffective against another.
“The evolution of SARS-CoV-2 variants upended many optimistic predictions made when
the vaccines were rolled out in 2020.”
— Dr. Arturo Casadevall
Despite the evolution of variants, vaccines still guard against severe COVID-19, particularly
in those who have received multiple vaccinations.
Despite suggestions that vaccines might even drive the evolution of new vaccine-resistant
variants, this does not seem to be the case, as a recent report states: “Given the
emergence of immunity-evading variants even before vaccines were broadly deployed, it is
hard to implicate vaccines or vaccine deployment strategies as the major drivers of immune
evasion.”
Prof. Stoye feels that vaccines will continue to be important. “I suspect we will have to have
yearly boosters of the vaccine, at least for the foreseeable future,” he said.
And he expressed a hope that research might create more powerful vaccines:
“It would be very nice if scientists could establish a pan-coronavirus vaccine that worked
against multiple viruses. That has to be one of the hopes of the future — that you will have
a method of vaccination that will protect you against various viruses.”
The end of the pandemic?

8. After 2 years, people are becoming tired of restrictions, feeling that the pandemic should
surely be over. However, Prof. Stoye is one of many experts expressing concern that
governments are removing COVID-19 testing and control measures too early.
“One of the things I’m frightened about is that we will, in fact, lose our ability to
follow these processes as we stop testing and sequencing so much. […] As we test
less, as we sequence less, we will lose that ability to recognize new variants in real
time,” he told us.
Global lessons for the future
“These things will come again. We need to realize that, and we need to have a response
ready quickly. I think we need to be able to recognize very rapidly the appearance of new
diseases — this comes back to geopolitics.”
— Prof. Jonathan Stoye
This is not the first pandemic, and it is unlikely to be the last. Some aspects have been well-
handled, while others have not, and the geopolitical debates will continue for years. At least
vaccines are continuing to protect against severe illness and death from all variants.
Possibly the most important lesson is that it is crucial to address future disease outbreaks
globally. Although people in high income countries have had ready access to vaccines and
boosters, many African countries have yet to vaccinate even 10% of their population due
to inequitable vaccine distribution.
The lack of widespread vaccination can also contribute to the development of new variants.
Prof. Stoye stressed the importance of global cooperation in countering pandemics:
“The global aspects of this are the interesting and important ones. Whether those lessons
will be learned, I don’t know. […] I would hate to think that, suppose in 2 or 3 years down
the track, we are living comfortably with this virus, and SARS-3 comes along or HIV5, and
we have forgotten all the lessons we have learned. It’s trying to retain that memory that is
the important lesson.”
Source : Medical NewsToday