A novel SARS-CoV-2 variant, the delta plus variant, has been identified in over 10 countries. Health authorities are raising concerns that the variant may have an increased ability to transmit, but they also note that this variant’s transmissibility is likely similar to that of the preexisting delta variant.

Why has the delta plus variant of SARS-CoV-2 caused some concerns, and what do we know about it so far? Image credit: DIPTENDU DUTTA/AFP via Getty Images

As ever more SARS-CoV-2 variants emerge, governments and public health experts continue to consider the best strategies to contain their spread. There are currently 11 variants of the SARS-CoV-2 virus that the World Health Organization (WHO) is monitoring.

One of these variants, the delta variant — also known as the B.1.617.2 lineage — was first identified in India in December 2020 and quickly became the most common variant in the country.

It has demonstrated 40–60% increased transmission, in comparison with the previously dominant alpha variant, and is currently the dominant SARS-CoV-2 variant in the United Kingdom.

Stay informed with live updates on the current COVID-19 outbreak and visit our coronavirus hub for more advice on prevention and treatment.

Meanwhile, researchers recently identified another variant — the delta plus variant, also known as B.1.617.2.1 or AY.1.

The U.K. governmental agency Public Health England first declared it a “variant of concern” in a June 11 briefing, and on June 22, Indian authorities followed suit.

Since then, 11 countries have reported a collective 197 cases of COVID-19 caused by the delta plus variant of SARS-COV-2.

The delta plus variant is a sublineage of the delta variant, with the only known difference being an additional mutation, K417N, in the virus’ spike protein, the protein that allows it to infect healthy cells.

This mutation is also found in the beta and gamma variants, which researchers first identified in South Africa and Brazil, respectively.

What risks does this variant pose?

The WHO shared with Reuters that “For the moment, this variant does not seem to be common, currently accounting for only a small fraction of the delta sequences.”

Yet, “Delta and other circulating variants of concern remain a higher public health risk, as they have demonstrated increases in transmission,” the WHO added.

Furthermore, since India has labeled this variant a “variant of concern,” the country’s SARS-CoV-2 Consortium on Genomics (INSACOG), which is made up of 28 laboratories dedicated to whole-genome sequencing of the SARS-CoV-2 virus and its evolving variants, continues to follow the evolution of delta plus.

INSACOG lists the following concerns regarding the delta plus variant:

• increased transmissibility
• stronger binding to receptors of lung cells
• potential reduction in monoclonal antibody response

The spike protein is responsible for binding to a cell’s surface receptors, allowing the virus to enter. A mutation in the protein may strengthen this interaction, which could increase transmissibility, as per these first two points.

This mutation, however, is present in other variants, as well, so it is likely not a new source of concern.

Additionally, virologist Dr. Jeremy Kamil, from the Louisiana State University Health Sciences Center, suggested to the BBC that “Delta plus might have a slight advantage at infecting and spreading between people who were previously infected earlier during the pandemic or who have weak or incomplete vaccine immunity.”

But he also noted that this is not much different from the delta variant.

Other experts have also raised the third point, about the variant’s potential to reduce the effectiveness of monoclonal antibody treatments.

These include therapies such as the bamlanivimab and etesevimab and REGN-COV2 combination therapies, which researchers have shown to be beneficial in treating mild to moderate COVID-19 when given early during the course of the disease.

However, this reduced effectiveness “is not a major difference, as the therapy itself is investigational and few are eligible for this treatment,” said epidemiologist and vaccine expert Dr. Chandrakant Lahariya in a CNBC interview.

Vaccine effectiveness

For the preexisting delta variant, many of the available COVID-19 vaccines show evidence of preventing hospitalization and severe disease.

The Pfizer and Oxford-AstraZeneca vaccines were highly effective, at respective 96% and 92% effectiveness after both doses. Studies on the Moderna and Covaxin vaccines also suggested they were able to neutralize this virus variant.

There are currently insufficient data on the vaccines’ effectiveness against the delta plus variant, but so far there have been no clear signs of the variant infecting people who have received the vaccination. Furthermore, no countries with cases of the variant have reported spikes in infection rates.

The Indian Council of Medical Research has isolated the variant to test vaccine effectiveness and has stated that results will be ready in the coming days.

While a new SARS-CoV-2 variant is inevitably concerning, there are no immediate indicators to suggest that delta plus is more infectious or dangerous than the other variants.

Further research and data from people with delta plus variant infections are needed to examine this variant’s characteristics and its ability to cause increased transmission or severity of COVID-19.

The delta variant of SARS-CoV-2: What do we know about it?

The variant of the SARS-CoV-2 virus called delta continues to spread rapidly across many parts of the world. What do we know about this variant so far?

What do scientists know about the fast-spreading delta variant of SARS-CoV-2? Image credit: Christopher Furlong/Getty Images

All data and statistics are based on publicly available data at the time of publication. Some information may be out of date. Visit our coronavirus hub and follow our live updates page for the most recent information on the COVID-19 pandemic.

The delta variant of SARS-CoV-2 — scientifically known as the B.1.617.2 lineage — was first identified by scientists in December 2020 in India.

In April 2021, the delta variant became the most commonly spread variant that caused new COVID-19 cases in India. Since then, this variant has been reported in 80 countries, according to the World Health Organization (WHO).

Recently, there have been concerns — particularly in the United Kingdom and the United States — that the delta variant could give rise to another COVID-19 wave, thus setting back national and international efforts to ease pandemic restrictions.

According to the latest report from Public Health England (PHE), the delta variant may have become the dominant variant in the U.K., with “74% of sequenced cases [of SARS-CoV-2 infection] and 96% of sequenced and genotyped cases” being caused by this variant.

In the U.S., data from the Centers for Disease Control and Prevention (CDC) put the proportion of new COVID-19 cases attributed to the delta variant at 2.7%. This is the most recent genomic surveillance data dating to the 2 weeks ending on May 22, 2021.

More recently, former Food and Drug Administration (FDA) Commissioner Dr. Scott Gottlieb has noted that around 10% of new COVID-19 cases are due to the delta variant.

Dr. Anthony S. Fauci, director of the National Institute of Allergy and Infectious Diseases, has reportedly warned that “any country that has the delta variant should be concerned that there will be a surge of infections, particularly if that particular country does not have a substantial proportion of their people vaccinated.”

“We’ve seen that when delta variant spreads among non-vaccinated people, it can become dominant very, very quickly,” he added.

How infectious is the delta variant?

Based on the data from the U.K., the delta variant is about 60% more transmissible than the alpha variant, which was previously called B.1.1.7. Alpha, in turn, is more transmissible than the strain previously dominant in the country.

Prof. Wendy Barclay, professor of virology and head of the Department of Infectious Disease at Imperial College London in the U.K., explained that this variant is more transmissible than previous ones because of some key mutations in the spike protein, which allows the virus to penetrate and infect healthy cells.

“The delta variant has got two important mutations in its spike protein, or sets of mutations,” she noted. “One is at the furin cleavage site, which we think is quite important for the fitness of the virus in the airway.”

“The virus that emerged in Wuhan was suboptimal in that respect, so it transmitted but perhaps not as well as it might. The alpha variant took one step towards improving that with a certain mutation, and the delta variant has built on that and taken a second step now, a bigger step, towards improving that feature,” said Prof. Barclay.

Are infection symptoms different?

Data collected by U.K. scientists also indicate that the primary symptoms of infection with the delta variant of SARS-CoV-2 are different compared with those experienced upon infection with previous variants.

Thus, data from the ZOE Covid Symptom Study — whose scientific analysis is conducted by experts from King’s College London — suggest that the main symptoms of infection with the delta variant are headaches, a sore throat, and a runny nose.

This is a change from official information on COVID-19 symptoms — such as that provided by the U.K.’s National Health Service (NHS) — that lists fever, continuous cough, and loss of smell or taste as the main symptoms of the condition.

Prof. Tim Spector, the co-founder of ZOE, warns that SARS-CoV-2 infections are “acting differently now, […] more like a bad cold,” which may tempt people to dismiss the symptoms.

“It might just feel like a bad cold or some funny ‘off’ feeling — but do stay at home and do get a test,” he urges.

What are the risks going forward?

Recently, a group of scientists called for the reintroduction of stricter safety measures in schools in the U.K. to curb the spread of the delta variant.

Given the data on delta’s increased transmissibility, some scientists have suggested that this may increase the risk of a further COVID-19 wave.

Modeling projections from Imperial College London indicate that the delta variant may significantly increase the risk of hospitalizations with COVID-19, exposing the U.K. to the possibility of a third wave, similar to the one the country experienced last winter.

Following concerning reports of the spread of this variant, the British government has already delayed the end of the pandemic restrictions in the country by 4 weeks.

Dr. Gottlieb also warned that the U.S. might experience further COVID-19 outbreaks because of this highly transmissible variant.

“I think in parts of the country where you have less vaccination, particularly in parts of the South, where you have some cities where vaccination rates are low, there’s a risk that you could see outbreaks with this new variant,” he suggested.

For this reason, he encouraged people to get fully vaccinated against COVID-19, noting that the vaccines currently authorized in the U.S. appear to hold up well against the emerging variant.

“The mRNA vaccine [Pfizer-BioNTech and Moderna] seems to be highly effective, two doses of that vaccine against this variant. The viral vector vaccines from [Johnson & Johnson] and AstraZeneca also appear to be effective, about 60% effective. The mRNA vaccines are about 88% effective. So we have the tools to control this and defeat it. We just need to use those tools,” he commented.