COVID-19: Delta variant: Here's what scientists know so far.
 |
| Courtesy of American Society for Microbiology |
Its origins
The new deadly strain B.1.617.2, called Delta variant by the WHO, first emerged in India in December 2020. As a testament to its highly contagious nature, the Delta variant has now been detected in sixty (60) countries world-wide, and counting. What makes Delta so different from other known variants? I'll explain.
Variants are identified by their mutations (i.e. alterations in the virus’s genetic material), and mutations in a virus are perfectly normal. For a RNA virus such as SARS-CoV-2, which is made of about 30,000 base pairs of amino acids, it is no different.
In fact, the Delta strain belongs to a mutated lineage of the virus called B.1.617 which is a specific type of SARS-CoV-2 variant. Apparently, the Delta strain is a sub-lineage —a branching off if you will, of the original mutation. It is therefore labelled B.1.617.2.
So what special features does B.1.617.2 have?
The Delta variant contains multiple mutations in the spike protein, at least four have been detected by scientists.
One of these is called L452R, first found by researchers in Denmark in March 2020, it makes the variant more transmissible i.e. it is easier to pass from one person to the other than other strains. This mutation has also been noted to diminish the strength of the coronavirus vaccine's neutralising antibodies.
The P681R mutation has been associated with chemical processes that may enhance transmissibility.
The D614G mutation was first reported in the US early in the pandemic, having initially circulated in Europe. A report from the Centers for Disease Prevention and Control (CDC) revealed: "There is evidence that variants with this mutation spread more quickly."
The fourth mutation in Delta is T478K. This was present in around 65% of occurrences in variant B.1.1.222, first detected in Mexico last year and is associated with higher infectivity.
All these changes to the spike protein make Delta a faster spreader and more better at manifesting symptoms and severe illness. Early evidence therefore suggests that this sub-lineage B.1.617.2, is more transmissible than other contemporary lineages.
More Transmissible
As a matter of fact, Andrea Ammon, director of the European Centre for Disease Prevention Control agency (ECDC) warns it is most likely that Delta will account for about 90% (ninety per cent) of new COVID-19 cases in Europe by August!
"The Delta variant is more transmissible than other circulating variants and we estimate that by the end of August it will represent 90 percent" of new cases in the EU, she said.
The director, noting how grave the situation could become during the summer months, revealed:
"It is very likely that the Delta variant will circulate extensively during the summer, particularly among younger individuals that are not targeted for vaccination".
The ECDC estimates that the Delta variant (B.1.617.2), is 40 to 60 percent more contagious than the Alpha strain (Î’.1.1.7) aka UK variant, which is currently the dominant strain of the virus circulating in the European Union.
The agency said that "70 percent of new SARS-CoV-2 infections are projected to be due to this [Delta] variant in the EU/EEA by early August and 90 percent of infections by the end of August".
Mass Vaccination
To counter the spread of the variant and mitigate the health impact, the ECDC said "it is very important to progress with the vaccine roll-out at a very high pace".
To date, about 30% (thirty per cent) of the adults over 80 years old and some 40% (forty per cent) of persons over 60 in the EU are still not fully vaccinated, according data from the ECDC.
"At this stage it becomes crucial that the second vaccination dose is administered within the minimum authorised interval from the first dose, to speed up the rate at which vulnerable individuals become protected," Ms. Ammon said.
The ECDC is also urging countries to be cautious about relaxing curbs aimed at limiting the spread.
"Any relaxation over the summer months of the stringency of non-pharmaceutical measures that were in place in the EU/EEA in early June could lead to a fast and significant increase in daily cases in all age groups," the agency said.
They fear this increase could in turn lead to a rise in "hospitalisations, and deaths, potentially reaching the same levels of the autumn of 2020 if no additional measures are taken."
UK numbers
In its August 2021 risk assessment for SARS-C0V-2 variants, Public Health England (PHE) has revealed that a worrying 61% of the samples sequenced are now of the Delta variant (B.1.617.2). In the week beginning May 17, PHE's analysis of genome sequencing data revealed this troubling information.
This means the Delta variant, first detected in India, is more dominant in the United Kingdom than the Alpha variant that first accounted for a large surge in cases last year. The Office for National Statistics reported that up to 12 of June, approximately one in every 540 persons is infected with the variant.
Update:
According to Public Health England data published on August 6, 2021, the Delta is the dominant strain across the UK, accounting for approximately 99% of cases. The data also included updated hospitalisations for Delta, which showed that in the period since the last update on 19 July, 1,467 people were hospitalised. Of these cases, 808 (55.1%) were unvaccinated, while 512 (34.9%) were fully vaccinated. While the vaccines may provide some amount of protection, they are not 100% effective and will not prevent everyone from catching COVID-19. In fact, experts say they expect that as more of the population gets vaccinated, there will be a corresponding increase in the number of vaccinated persons who will be hospitalized.
Variant of Concern
On May 10, 2021, the World Health Organizaton (WHO) categorised it as a variant of concern (VOC). It also said it continues to observe "significantly increased transmissibility" and a "growing number of countries reporting outbreaks associated with this variant".
The WHO classifies a variant as a VOC when it is associated with an increase in transmissibility or detrimental change in Covid-19 epidemiology; increase in virulence; or decrease in the effectiveness of public health measures or available diagnostics, vaccines, therapeutics.
Public Health England said Delta continues to demonstrate a substantially increased growth rate compared to Alpha across multiple analyses. In fact, it noted that as Delta cases are rising Alpha case numbers are on the decline. Delta cases are said to now account for over 90% (ninety per cent) of new infections in the United Kingdom.
Hospitalizations
The PHE agency said early evidence from England and Scotland suggests there "may be an increased risk of hospitalisation compared to Alpha cases".
Additionally:
"A large number of cases are still within the follow-up period. In some areas, hospital admissions show early signs of increasing, but the national trend is not clear," it said.
Threat to the U.S.
Cases of the variant are rising in the U.S. and according to the CDC, account for about 6% (six per cent) of new coronavirus infections.
Update: Fox5 reported CDC data which revealed that as of August 2021, the Delta variants accounted for 93% of US cases. According to the news network "the primary delta variant, known as the lineage B1.617.2, makes up 83.4% of COVID-19 cases. But when combined with its sublineages, that number grows to 93.4%".
Dr. Anthony Fauci, speaking at a recent White House COVID-19 briefing, warned this strain could cause more severe illness and higher risk of hospitalization. Dr. Fauci also urged persons who received the first shot of the Pfizer or Moderna vaccine to sign up for the second shot, after the latest PHE study revealed that though one dose of the Pfizer-Biontech vaccine had an efficacy rate of only 33%, two doses had an increased efficacy of 88%.
Vaccine efficacy
The Public Health England (PHE) study, which used data from England and Scotland, revealed evidence of a reduction in vaccine effectiveness for Delta compared to Alpha. Pfizer was 93% effective against the Alpha strain, but fell to 88% against Delta, even after two doses of the vaccine. This is more pronounced after one dose —efficacy rate plummeted to 33% after only one jab.
The PHE said:
"Iterated analysis continues to show vaccine effectiveness against Delta is higher after 2 doses but that there is a reduction for Delta compared to Alpha".
A recent study published by The Lancet (science journal) said adults fully vaccinated with the Pfizer-BioNTech vaccine may have extremely lower levels of neutralising antibodies (five (5) times lower) against the Delta variant compared to other variants. "In the longer term, we note that both increased age and time since the second dose of BNT162b2 significantly correlate with decreased NAb activity against B.1.617.2 and B.1.351—both of which are also characteristic of the population in the UK at highest risk of severe Covid-19," the study states. They also noted that the Delta variant was now the dominant strain in Scotland, replacing the Alpha variant.
Delta variant and reinfection
The latest analysis of 874 cases of reinfection in the UK shows that 556 were of Alpha variant, and only 96 were with the Delta variant. "During the period of time that Delta became prevalent, there has been no increase in PCR-positive participants in the… cohort overall and reinfections remain at very low numbers in individuals previously either PCR positive or seropositive," the PHE said. Which means so far, the UK variant (Alpha) though declining, is still the dominant strain in the United Kingdom overall, though this is changing rapidly.
The emerging Delta Plus mutant
There has been a new development in the Delta variant's gene pool. Delta Plus (B.1.617.2.1/(AY.1) emerged as a result of mutation in the K417N spike protein. This mutation makes the virus more resistant to what is called monoclonal antibodies, which are human manufactured antibodies that are cloned from a specific white blood cell. The new mutation increases the virus' infectivity, allowing it to pass easily into human cells and cause an infection.
According to Dr. Shuchin Bajaj, internal medicine, founder-director of the Ujala Cygnus Group of Hospitals, the new Delta Plus variant "at present, is limited to smaller areas in the country [India]. This mutant of Delta was first detected in Europe in March 2021, but it came to light on June 13. Although it is still under investigation, experts believe that the Delta Plus variant has increased transmissibility".
Already, this new version of the variant has been detected in several Indian states: Maharashtra, Kerala, and Madhya Pradesh, Punjab, Tamil Nadu, and Andhra Pradesh. The health ministry has advised the states government officials to impose strict containment measures in the affected districts.
Additionally, Delta Plus has so far migrated to over 80 countries including the US, UK, Portugal, Switzerland, Japan, Nepal, Poland, China and Russia.
Update: According to the W.H.O. the Delta has been detected in over 130 countries according to W.H.O. in an August 3 COVID-19 Weekly Epidemiology Update. See more info here. By August 24 the number had jumped to over 140 countries.
Conclusion
The Delta variant is proving to be a super mutation of the novel coronavirus. Scientists are still learning about this new variant and have recently discovered that it has a sub-variant called Delta Plus. Delta or its offspring Delta Plus are even more transmissible than the Alpha strain and has been linked to an upsurge in cases both in Europe and the United States. This new mutant is capable of bypassing the human body's defenses, reducing the effectiveness of the immune system's antibodies, and diminishing the neutralizing properties of the current COVID-19 vaccines leading to possibly more severe illness and hospitalizations.
Way forward?
No doubt, more research will be done to unlock the full secrets of this new variant and how to beat it. In the mean time, protect yourself by wearing your mask, sanitizing, building up your immune system and when the vaccine is available to you, and if you wish to, get vaccinated.
All the best folks. Keep safe. 😊
(Article updated August 26, 2021).
_______________
References
Roberts, Michelle. UK Covid infections rise as Delta variant dominates. BBC News online, published June 19, 2021. https://www.bbc.com/news/health-57525891
Sheriff M, Kuanain. Explained: What is the Delta variant of Covid-19, and whiy is it a concern, Indian Express, published June 24, 2021, https://indianexpress.com/article/explained/covid-delta-variant-coronavirus-cases-7344758/
Greenhalgh, Jane. The highly contagious Delta variant is on the rise in the US, National Public Radio (NPR), published June 8, 2021, https://www.npr.org/sections/coronavirus-live-updates/2021/06/08/1004597294/the-highly-contagious-delta-variant-of-covid-is-on-the-rise-in-the-u-s
Wall, Emma C et al. Neutralising antibody activity against SARS-CoV-2 VOCs B.1.617.2 and B.1.351 by BNT162b2 vaccination, The Lancet, published June 3, 2021, https://www.thelancet.com/journals/lancet/article/PIIS0140-6736(21)01290-3/fulltext
Sheikh, Aziz et al. SARS-CoV-2 Delta VOC in Scotland: Demographics, risk of hospital admission, and vaccine effectiveness, The Lancet, published June 14, 2021, https://www.thelancet.com/journals/lancet/article/PIIS0140-6736(21)01358-1/fulltext
Lifestyle Desk. Covid-19 Delta Plus variant: Important things you need to know, Indian Express, published June 24, 2021, https://indianexpress.com/article/lifestyle/health/covid-19-delta-plus-variant-know-pandemic-covid-third-wave-7374210/
Comments
Post a Comment