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There are many variants of the
coronavirus
, but those in which the attention of scientists (and health authorities) converges are called
VOCs
: literally from English "worrisome variants".
There are four:
Alpha, Beta, Gamma and Delta
.
Then there are the
VOIs
, the "variants of interest":
Eta, Iota, Kappa and Lambda
and finally some others, which for now only named with letters and numbers of the genetic classification.
The names
Before June, the variants were named after
the country
where they were first identified: there were
English, South African, Brazilian and Indian
.
Since June, the
World Health Organization
(WHO) has decided to name all the variants under its analysis (VOC and VOI) and a name with the
letters of the Greek alphabet
, in the chronological order in which they were designated as potential threats, to avoid stigmatizing geographically.
Names or numbers that are difficult to use and distinguish.
What makes them "successful"
The 'variant' is
the new genetic code
of a virus that has acquired one or more mutations, which in turn are the
variations
that change the characteristics of the virus itself.
The mutation is the cause and the variant is the effect.
The variants, despite the similarities, appear to have
arisen completely independently of
each other, but they often have
similar mutations
, as if the virus found the "best" ways to enter the body on its own.
The most efficient (and therefore dangerous) variants are those that involve the outer protein, the spike protein, that attaches itself to human cells.
Of the
SARS-COV-2
strain
, originally from Wuhan, the
"winning"
variants
have always been the
most contagious
, compared to the most pathogenic, in line with the virus's main interest: to replicate and spread.
The first
The first noteworthy variant is the strain that Europe has distinguished itself from the
original Wuhan
.
Then called
"D614G"
, the variant appeared in
Europe
in February and March 2020 and became prevalent worldwide in June, with
a transmission capacity of up to 10 times greater
than the Chinese strain.
A second variant (called
"20A.EU1"
) appeared in June 2020 in the northeast of
Spain
and quickly spread to the rest of Europe, contributing to the
second wave
(that of autumn).
Alpha variant
Then came the "worrying" ones:
Alpha was identified
on September 14, 2020 in
the UK
. Now widespread in 154 countries, it has gradually become widespread in
Europe
, the
United States
,
Canada,
and
Japan
.
Alfa has supplanted the other variants also in Italy becoming dominant until a few weeks ago.
It is now the source of most new infections in the US.
Alpha has 23 mutations, including 8 in the Spike protein (including
N501Y
), that make it more transmissible, on the order of at least
50% more
than the original strain.
Research has shown that the
variant
is associated with a
higher viral load
, but it does not appear to have a greater severity of
Covid
disease
.
The efficacy of the vaccines
used in Europe and Great Britain (Pfizer, Moderna and AstraZeneca)
does not weaken
against Alpha.
Beta variant
The
Beta
variant
emerged in South Africa
in September 2020. It has largely been confined to South Africa, although 102 countries have recorded at least one case. The most reported state after South Africa is France, with 3,048 cases.
The
Beta variant
shares the
N501Y
mutation
in the spike protein with Alpha. It has
21 mutations
in total, 9 in this protein.
It is less transmissible than
Alpha, but it is still
the variant with the immune-evading potential of the main vaccine, comparable to Delta
. This is due to a mutation,
E484K
, which would confer this characteristic on it.
The effect of reducing vaccine protection cannot be quantified with a single number, because it is measured differently depending on the studies and the countries that hosted the research.
The efficacy of the vaccines decreases
with Beta in protecting against infections, especially after 1 dose, but remains high for all
vaccines
with respect to hospitalizations (after 2 doses).
Gamma variant
In October 2020,
the variant called Gamma was identified in Brazil
.
Spread in 62 countries, especially in
South America
, it also reached the US, Canada and Europe, including Italy, where it was the second variant in order of prevalence for a period (definitely separated from Alpha and always below 10%).
Outside of the South American countries, which nevertheless use
Chinese vaccines
(less effective), it has not been able to "prevail" on
Alpha
and
Delta
. It contains a
unique constellation of mutations
, including
N501Y
, common to Alpha, and
E484K
, common to Beta, the most concerning for
vaccines
.
Gamma has been calculated to be
between 1.4 and 2.2 times more transmissible
compared to the
"archaic"
coronavirus
, slightly less contagious than the Alpha variant.
Compared to the
efficacy of vaccines, it has a minimal reduction
It is somewhere between Alpha (which does not cause efficacy problems) and Beta, but studies done on
Gamma
often do not involve vaccines used in Europe or the USA.
Delta variant
In September 2020,
the variant initially named B.1.617 was identified in India.
The
B.1.617
strain
continued to evolve,
dividing into new variants, including B.1.617.1, known as Kappa (VOI), and B.1.617.2, known as Delta.
It is the latter that has spread to
105 countries
, but in Europe it has overtaken any other
variant
that is becoming predominant (first in the UK and now also in Italy). Due to a number of characteristics, it could also become dominant in the rest of the world.
Delta
has been erroneously called a "double mutant" because, in addition to the 10 mutations it presents, it contains two known mutations,
E484Q and L452R
, appearing together for the first time. The first is common to the
widespread
Epsilon variant
in California and would be the cause of the greater contagion capacity, the second confers the partial immune evasion power of vaccines.
Delta
is approximately
50-70% more transmissible than the Alpha variant
, which in turn was 50% more transmissible than the strain that was in Europe last year. According to the first studies, the mechanism that underlies this
formidable contagion
is a process that implies the
reduction of the incubation time
(from 6 days on average to 4) and the
increase of the viral load
, measured at least 1,000 times higher (compared to the Wuhan virus) from day one.
According to a Scottish study published in
The Lancet
on June 14, the
Delta variant
is associated with roughly
twice as many hospitalizations as the Alpha variant
, but these are data to be confirmed.
It presents
slightly different symptoms
: headache, sore throat, runny nose and fever (for the other variants there are no differences with the archaic virus). Cough is rarer, and loss of smell is not even among the top 10 symptoms.
The efficacy of vaccines against Delta drops, especially after a single dose and especially with regard to infections. The
vaccines
offer good coverage after two doses and protect well against hospitalization or death, so much so that, with respect to
Delta's
advance
, there is talk of
"an epidemic of the unvaccinated
.
"
In ascending order on a scale from 1 to 100 we can say that, with the
Delta variant
, those who are not vaccinated have zero protection, those who have taken a dose are protected by 20-30%, those who are cured by 60 -70%, who has received two doses of the vaccine is 70-80% and who has had the disease and then the vaccine is probably 90%.
Vaccinated people can reinfect themselves
(about 12% chance) but will not develop a serious disease.
They can be contagious
, but less, especially if they meet other vaccinated.
The new variants under observation
The WHO classifies four other variants as of "interest".
Kappa
is the strain that comes from Delta, certainly less contagious and less worrisome.
Eta
was detected in
Nigeria
in December 2020: it has the
E484K
mutation
, it reached 69 countries without prevailing (some cases also in Italy).
Iota
spread rapidly to
New York City
as of November 2020. It has remained primarily in the US It has the
E484K
mutation
.
Lambda
was first identified in
Peru
in August 2020. Detected in 29 countries, it has high levels of diffusion in America: 33% in Chile, 23% in Peru, 20% in the United States.
Lambda
has three "dangerous" mutations:
T76I
and
L452Q would
increase the contagion power, in fact L452R is common to the variant that has spread in California (Epsilon), known to be more transmissible.
The third mutation is indicated with
RSYLTPGD246-253N
: it is found in the terminal part of the spike protein and thanks to it
Lambda
could have the power to escape the antibodies created by
vaccines
, but according to the first studies it would be a "modest" resistance , suggesting that
vaccines
they can work the same.
According to the criteria of The Trust Project
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