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The Delta Variant

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The Delta Variant

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Learn more about the Delta variant, the symptoms, and how effective vaccines are against it.

Medically reviewed by

Dr. Mervin Raj. M

Published At June 26, 2021
Reviewed AtMarch 21, 2023


The second COVID wave was at its peak in July 2021 and health experts reached a decision that the surge in COVID-19 cases in mid-2021 was due to the Delta variant. The virus (SARS-CoV-2) is surprising us with new variants. It is beyond anything that health experts expected.

The Delta variant of the Coronavirus was first reported in India. It created a peak in cases in some parts of the United Kingdom and the United States. Soon this grabbed the attention of health experts worldwide. This variant was named Delta by the World Health Organization (WHO). Health experts considered this to be more transmissible than the other variants. This article will brief you through some information about the variants of SARS-CoV-2.

Why Are There Such New Variants Emerging?

All viruses, including SARS-CoV-2, change over time. These changes can have little or no impact on the properties of the virus. However, some changes affect the properties of the virus, how easily it spreads, the severity of the diseases associated with it, and the performance of the vaccines and therapeutic medicines.

Does SARS-CoV-2 Meet the WHO Definition of Variants of Concern?

Since late 2020 and until now, the emergence of new variants is posing an increased risk to global public health. Hence the World Health Organization has come up with the characterization of variants in order to prioritize global monitoring and research and to inform about the ongoing response to the COVID-19 pandemic.

The SARS-CoV-2 variants definition of the variant of interest:

  • Increase in the transmissibility or change in the epidemiology of COVID-19.

  • Increase in the clinical disease presentation or increase in the virulence.

  • Decrease in the effectiveness of vaccines, social measures or therapeutics.

What Are the Different Variants of SARS-CoV-2?

Viruses change over time through the process of mutation. The different variants are:

  • B.1.1.7 - This is called the Alpha variant, which was first seen in the United Kingdom.

  • B.1.351 - This is called the Beta variant, which was first seen in South Africa.

  • P.1 - This is called the Gamma variant, first seen in Brazil.

  • B.1.427 and B.1.429 - This variant is called the Epsilon.

  • B.1.617.2 - Delta variant first noticed in India, circulating in the United States.

  • B.1.1.529, BA.1, BA.1.1, BA.2, BA.3, BA.4 and BA.5 lineages - Omicron variant.

How Do These Variants Occur?

Viruses constantly change through mutation, and new variants are expected to occur. Sometimes new variants emerge and disappear. Other times the new variants usually persist. It is one of the natures of RNA viruses to evolve and change gradually. Geographic separation tends to result in genetically distinct variants. Mutation in viruses is neither new nor unexpected. All RNA viruses mutate over time.

How Does Mutation Occur?

When a virus infects the host cell, the genetic material gets copied to be put into the new viruses. These new viruses are gradually released from the host cell and can go on to infect new cells. Viruses use an enzyme polymerase to copy their genetic material. These polymerase enzymes are not perfect, and they can make mistakes. These mistakes result in a mutation. Usually, the mutation does nothing, but sometimes it can be harmful to the virus. When the mutations are harmful, they can affect the virus‘s ability to infect or multiply within a host cell.

In certain cases, mutation gives a newly produced virus an advantage to bind more tightly to the host cell, or it helps escape the immune system. When this happens, variants can become more common among the population. This is what is happening with the new variants of SARS-CoV-2.

What Is Delta Variant?

Delta Variant is a variant of SARS-CoV-2. It is known as the lineage B.1.617.2 and is a variant of lineage B.I.617 of SARS-CoV-2. It was first detected in India in late 2020. The name Delta was given by the World Health Organization (WHO). The Delta variant is also referred to as “Double mutant” due to the presence of mutations E484Q and L452R. Double mutation refers to B.1617’s mutation in the gene encoding the SARS-CoV-2 spike protein.

Is Delta Variant More Dangerous?

The Delta variant is more transmissible than the other variants. It not only spreads more easily, but it can also cause severe disease. Unvaccinated people and people with weakened immune systems are more prone to this variant. It is also known to cause breakthrough infections in vaccinated individuals.

What Are the Symptoms of the Delta Variant?

The classic symptoms of COVID are:

The most commonly noticed symptoms in the United Kingdom, when there were about 91% of new cases with the Delta variant, were:

The viral loads in the affected individuals were higher than previously seen variants during this pandemic. And most people become severely ill within 3 to 4 days of getting infected with the virus. However, those people who are asymptomatic can still transmit the virus to others.

Why Is the Delta Variant More Concerning?

It is noticed that the Delta variant carries the genetic code from other mutations, E484Q and L452R, so it is easy for it to break into the human immune system and invade the organs in the body. Moreover, this Delta variant has the ability to alter the structure of the spike protein, and it is also more efficient in attaching itself to the host cells and multiplies swiftly, causing more damage than the other previous COVID variants.

What Is the Difference Between Delta Variant and Other Variants?

  • The delta variant transmits much easier as compared to other variants and impacts the younger population more in the age of 30 to 60.
  • It is highly contagious and can cause severe illness in unvaccinated people as compared to other variants.
  • It can also be transmitted by fully vaccinated people but it is seen rare as compared to unvaccinated people.
  • The patient infected with Delta variant can be detected four days after the exposure, however, the original variant was detected after six days. Moreover, the people infected with the delta variant remain contagious for about 18 days as compared to the original strain which was 13 days.

Do COVID Vaccines Have the Same Effectiveness Against the Delta Variant?

In a study, it was found that the antibody levels in people with two doses of Pfizer-BioNTech shot were known to be six times lower in the presence of the Delta variant than in the presence of the other variants in people who were given the COVID vaccine. So in the study, it was reported that neutralizing antibodies produced by vaccination with Pfizer-BioNTech are three to ix times less effective against the Delta variant than against the Alpha variant. However, the severe illness and death by Delta variant have been prevented by all vaccines approved by W.H.O, yet, no vaccine is 100 % effective and milder symptoms may appear even in fully vaccinated people. It is highly imperative to have both doses and booster doses of vaccines to get the maximum protection.

Are the Vaccines Still Working Against the Delta Variant?

Though the levels of antibodies are not enough to determine the effectiveness of the vaccine, which is an important marker, it is found that all approved vaccines by W.H.O are effective in preventing hospitalizations against the Delta variant. The rise in the number of cases will eventually lead to an increase in breakthrough infections.

Delta Plus Variant:

The delta variant is feared to have mutated into a more virulent version called Delta Plus or AY.1. It is said to be resistant to the monoclonal antibodies cocktail. It is characterized by the acquisition of K417N mutation. The mutation is in the spike protein of SARS-CoV-2, which helps the virus to enter human cells and infect them. The sequences are mostly from Europe, Asia, and America. The earliest sequence was found in Europe. This K417N mutation is also found in the Beta variant, which is considered to be a variant of concern.

When errors happen in the replication of viruses, the virus gets a new character. Not all these errors are alarming, but the health experts are still tracking these mutations. Studies are going on, and more variants are under observation. Whether or not these new variants will take over the parent to cause new waves depends on the global vaccination percentage and their efficacy. .


The surge in COVID-19 cases during the second wave could be attributed to the Delta variant. Delta variant was the factor that drove the increase in the number of COVID-19 hospitalization and deaths. So it is indispensable to get vaccinated timely even with booster doses and follow the safety guideline and beat this pandemic.

Frequently Asked Questions


What Is the New Delta Variant Mutation?

The WHO classified the Delta version (B. 1.617. 2), found in October 2020, as a VOC on May 11, 2021. Critical S-protein mutations, including D614G, L452R, P681R, and T478K, have been linked to the increased transmissibility of the Delta form.


What Does Delta Plus Variant Mean?

If vaccinated people develop the delta variant, they typically exhibit no symptoms or perhaps minor symptoms. Their symptoms, which can include a substantial loss of smell, are more similar to an ordinary cold, such as cough, fever, or headache.


Is the Omicron Variant the Same as Sars-Cov-2?

The Omicron version of the severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2) is circulating worldwide. The World Health Organization has classified this variety as a virus with significant mutations and a variant of concern (WHO).


What Does the Acronym Sars-Cov-2 Mean?

It means Severe Acute Respiratory Syndrome coronavirus 2.


Is the Delta Variant More Severe?

Compared to the other viral strains, Delta is more infectious. As a result, the CDC classified the Delta strain as "a variant of concern," using the same classification as the strains that originally erupted in South Africa, Great Britain, Brazil, Alpha, Beta, and Gamma.


Why Does the Delta Variant Spread More Easily?

It becomes even simpler for the delta variation to penetrate the human immune system and infect the organs, considering that it bears the genetic material from two additional mutations, E484Q and L452R.


What Causes Concern With Delta Variant?

The COVID-19 delta variant's symptoms resemble the original COVID-19 in many ways. However, doctors notice that patients are becoming sicker more quickly, particularly younger people. According to recent studies, the delta version grows more rapidly and to significantly higher levels in the respiratory system.


How Resembling Is SARS To COVID-19?

Concerning its clinical characteristics, COVID-19 doesn't differ significantly from SARS. However, it has a fatality rate of 2.3 %, substantially lower than MERS's (34.4 %) and lower than SARS's (9.5 %).
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Dr. Mervin Raj. M
Dr. Mervin Raj. M

General Practitioner


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