SARS-CoV-2 Delta variant

Delta variant

The Delta variant (B.1.617.2) was a type of SARS-CoV-2, the virus that causes COVID-19. It was first found in India on 5 October 2020. By May 2021, it had spread to many countries and became the most common form of the virus worldwide.

This variant had special changes that made it spread more easily between people. It also made it harder for the body to fight the virus. Even people who had been sick with COVID-19 before or had gotten vaccines were still safer from getting very ill, but the Delta variant could still cause infections.

The Delta variant made the pandemic worse in many places. It helped cause big increases in cases in India, the United Kingdom, South Africa, and many other countries. Health experts worked hard to learn how to protect people from this stronger version of the virus.

Classification

The Delta variant had special changes in a part of the virus called the spike protein. These changes were D614G, T478K, P681R, and L452R. Scientists called it part of the 21A, 21I, and 21J clades.

The Delta variant was first found in India and was called the "Indian Variant" by some people. It was one of three variants from a group called lineage B.1.617.

In May 2021, the World Health Organization started using Greek letters like Delta to name important variants.

There were three types of lineage B.1.617. One was called the Kappa variant Kappa variant. The Delta variant, also known as B.1.617.2, had some changes but not all the changes found in the other types.

The Delta variant had at least 13 changes in its genetic makeup. Four of these changes were especially important because they were in the spike protein:

• D614G, a change shared with other versions of the virus.
• T478K, another change in the spike protein.
• L452R, which helped the virus stick better to cells.
• P681R, which may have helped the virus infect cells more effectively.

The Delta variant did not have a change called E484Q.

By August 2021, scientists had found many versions of the Delta variant, named from AY.1 to AY.28. These versions were found in many countries. One version, called "Delta plus" or "Nepal variant," had an extra change called K417N.

In October 2021, a version called AY.4.2 was found to spread a bit faster than the original Delta variant.

Symptoms

Main article: Symptoms of COVID-19

The Delta variant of the virus that causes COVID-19 usually causes symptoms like other versions of the virus. Common signs include fever, a dry cough, feeling weak, coughing up mucus, headaches, trouble breathing, and muscle aches. Many people first notice they cannot smell or taste things. In more serious cases, breathing problems can appear later. Some people may also face very serious health issues.

Prevention

See also: COVID-19 § Prevention, Oxford–AstraZeneca COVID-19 vaccine § Effectiveness, Pfizer–BioNTech COVID-19 vaccine § Effectiveness, Moderna COVID-19 vaccine § Effectiveness, Janssen COVID-19 vaccine § Clinical trials, Sinopharm BIBP COVID-19 vaccine § Variants, Sputnik V COVID-19 vaccine § Effectiveness, CoronaVac § Variants, Covaxin § Efficacy, ZF2001 § Efficacy, and Abdala (vaccine) § Efficacy

The World Health Organization did not make new rules to stop the Delta version of the virus. The same safety steps that help stop regular COVID-19 still work. These steps include washing hands often, wearing masks, staying away from others, not touching your face, and avoiding crowded places with poor air flow. If you feel sick, it is important to get tested and rest if you are told you are sick. Health workers should find people who might be sick, tell their close contacts, and help those who are sick rest and recover.

Studies show that vaccines like Covaxin, Covishield, Pfizer-BioNTech, and AstraZeneca-Oxford help protect people from getting very sick with the Delta version of the virus. Even though the virus can sometimes spread to people who are vaccinated, the vaccines still help stop serious illness and hospital stays. Experts believe these vaccines are very good at keeping people safe from the worst effects of the Delta version.

Summary of vaccine protection against Delta
(WHO's update, 24 August 2021)

Disease or infection	Severe: protection retained Symptomatic: possibly reduced protection
Severe disease	: AstraZeneca-Vaxzevria(1), Moderna(1), Pfizer-BioNTech(2)
Symptomatic disease	to : Pfizer-BioNTech(3) : Covaxin(1) : AstraZeneca-Vaxzevria(2)
Infection	: AstraZeneca-Vaxzevria(1), Pfizer-BioNTech(1)
Symbols indicate the magnitude of vaccine effectiveness (VE) reduction. Note that VE reduction doesn't mean loss of protection, because original high protection rate (such as 95%) with some reduction (such as 10%) would still retain protection (such as 85%). Enclosed in parentheses is the number of studies supporting the indication. Studies vary in population, outcome definitions, study design, etc., which may explain differences in VE estimates for a product in different studies. Also, the reductions represent VE estimates and do not represent uncertainties around the estimates which may vary substantially across studies. The VE reductions should be interpreted with these limitations. : VE reduces 90% without comparator : VE reduces between 10 and : VE reduces between 20 and

Effects on neutralization (fully vaccinated)
to : Anhui-ZIFIVAX(2), Covaxin(3) : Janssen(3), Moderna(3), Covishield(2) to : AstraZeneca-Vaxzevria(4), Pfizer-BioNTech(8) :Moderna & Pfizer-BioNTech(1)* to : Coronavac(2)
Symbols indicate the magnitude of neutralization reduction with full vaccination. Enclosed in parentheses is the number of studies supporting the indication. : Neutralization reduces : Neutralization reduces 2 to : Neutralization reduces 5 to : Neutralization reduces ≥ 10-fold * Moderna & Pfizer-BioNTech were evaluated together.

Treatment

See also: Treatment and management of COVID-19

Some medicines may not work as well against the Delta variant of the virus that causes COVID-19. Research shows that treatments like casirivimab, etesevimab, and imdevimab can still help, as well as another treatment called sotrovimab. In places like Singapore, doctors have used extra oxygen, remdesivir, and corticosteroids to treat people with this version of the virus more often.

Epidemiology

Transmissibility

Scientists in the UK found that the Delta variant spreads more easily than earlier versions of the virus. It is thought to be more contagious than the Alpha variant, which was already very spreadable. This means the Delta variant can reach more people faster. Even people who are vaccinated can still catch the Delta variant, though they are less likely to get very sick from it.

Infection age groups

Data from India showed that during a wave of COVID-19, more younger people, especially those under 30, were getting infected. Hospitals also saw more young adults needing care.

Virulence

Some early studies suggested the Delta variant could make people more sick than other versions of the virus. Reports from different countries found that people with the Delta variant were more likely to need hospital care.

Statistics

The chance of finding cases of the Delta variant depends on how often a country checks the virus for changes. Some countries check very few cases, while others check about half of their cases.

By 22 June 2021, more than 4,500 examples of the Delta variant had been found in about 78 countries. The numbers from each country are shown below.

History

The Delta variant of the virus that causes COVID-19 was first found outside India in late February 2021. It was seen in the United Kingdom on February 22, the United States on February 23, and Singapore on February 26.

British scientists renamed the B.1.617.2 variant to "variant of concern" in May 2021 because it spread faster than the original virus. They noticed it was spreading quickly in communities. By early June 2021, it became the most common version of the virus in the UK. It was also found to spread more easily between people in households than earlier versions.

Other countries also found the Delta variant. Canada identified its first case in Quebec on April 21, 2021, with more cases later in British Columbia, Alberta, and Nova Scotia. Fiji confirmed its first case in Lautoka on April 19, 2021. The variant was also detected in Finland, the Philippines, and North Macedonia in the months that followed.

By July 2021, the Delta variant became the most common version of the virus in many places, including the United States and parts of Europe.

Extinction

In October 2021, a leader from the UK Health and Security Agency said that earlier virus versions like Alpha had mostly gone away, replaced by the Delta version. By March 2022, groups like the World Health Organization said Alpha, Beta, and Gamma were no longer being found. This happened because Delta and then the Omicron version became more common. Soon after, Omicron became the main version, and Delta was found much less often. Some mixes of Delta and Omicron, called "Deltacron" by Leondios G. Kostrikis, appeared for a short time, but Omicron eventually made Delta almost disappear.