The Delta variant of the coronavirus (B.1.617), with a first case documented in India in October 2020 and classified by the World Health Organization as a variant of concern (VOC, English) in May 2021, has been detected in more out of 80 countries so far, according to WHO.
So far, the WHO has identified four VOCs (Variant of Concern): Alpha (B.1.1.7), Beta (B.1.351), Gamma (P.1) and Delta.
Reports have also appeared of a more infectious sublineage of the Delta variant, sometimes referred to as Delta Plus or AY.1. This variant has the K417N mutation, which is commonly seen in the Beta variant first identified in South Africa.
At the moment, there are not many cases of this variant, according to PANGO Lineages, a website created by scientists that allows users to assign the most probable lineages to SARS-CoV-2 sequences.
“This is a mutation that has possibly been re-associated with better ability to evade vaccines and with increased transmissibility,” said Deepti Gurdasani, an epidemiologist at Queen Mary University, London.
Like all variants, Delta also accumulates mutations with relative ease, so much so that it soon gave rise to a kind of “family”, with three versions called B-1617-1, B-1617-2 and B-1.617-3.
Of these, the most widespread is B-1617-2, considered 60% more efficient in transmission than the Alpha variant thanks to some mutations, such as K417N, also present in the Gamma variant, the Beta identified in South Africa and the E- 484Q, also present in the Gamma variant. The B-1617-2 variant has now also changed, by developing a new version, indicated by the initials B-1617-2-1 or, more simply, AY-1.
It’s important to remember that viruses have many mutations, said Francois Balloux, director of the Institute of Genetics at University College London.
In the UK, the Delta variant has been detected more than 46,000 times (as of June 18), according to GISAID, a scientific initiative to facilitate data sharing. That is the largest number of Delta cases identified in a country so far.
Data from PHE, an agency of the UK Department of Health, indicates that more than 90% of new COVID-19 cases in the region are of the Delta variant.
The UK had confirmed more than 42,000 cases of the Delta variant as of June 9, with an increase of nearly 30,000 reported from June 2-9, according to PHE data. Of the PHE-confirmed cases, the majority were either unvaccinated or had only received one dose of the vaccine.
PHE research found that the Delta variant is associated with a 64% higher chance of transmission at home compared to the Alpha variant (B.1.1.7) first identified in the UK.
“What we noticed at the beginning in India was that the Delta variant was outpacing or growing faster than the so-called Kent or Alpha variant, which first originated in the UK,” Gurdasani said, “and this was very concerning because We knew at that time that the Alpha variant was already more transmissible than the original virus ”.
If the transmissibility of a variant is 50-60% higher than that of a previous variant, which was also 60% more transmissible than a previous virus, we are facing an increase in transmissibility that could be up to three times, said Gurdasani.
Maria Van Kerkhove, WHO COVID-19 technical director, said on Twitter that the Delta variant is more transmissible than the Alpha variant and the original coronavirus.
However, there is still little data available on whether the Delta variant causes more deaths.
Between February 1 and June 7 there were 42 deaths caused by the Delta variant in the UK. Of these, 23 people were not vaccinated, seven died more than 21 days after their first dose of vaccine, and 12 died more than two weeks after their second dose.
Compared to the Alpha variant, the Delta variant is more likely to cause hospitalization, according to PHE. More than 1,300 people were hospitalized for all variants of COVID-19 from June 7 to 13, an increase of 43% compared to the previous week.
“UK data tell us that it is more likely to cause hospitalization, so it would not be surprising if it were found to be more deadly,” Gurdasani said.
The high transmissibility of a virus leads to a faster increase in cases, which ultimately means more hospitalizations and deaths, Gurdasani said. Vaccination will help, but many people around the world are still waiting for their shots.
There are other factors that can also influence a person dying from a virus, such as comorbidities and socioeconomic determinants. “It is very difficult to measure because there are many confounding variables,” Balloux said. But we need more information to know if it is really the variant itself or is it a combination of factors.
A study by the UK agency PHE, pending review, found that two doses of COVID-19 vaccines are highly effective in preventing hospitalization.
The Pfizer-BioNTech vaccine was found to be 94% effective against hospitalization after one dose and 96% effective against hospitalization after two doses. AstraZeneca’s was 71% effective after one dose and 92% after two.
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