Variants of SARS-CoV-2

Variants of severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2) are versions of the virus that causes coronavirus disease 2019 (COVID-19). These variants look similar to the original virus but have small changes that make them slightly different. Scientists study these differences.

Some variants can spread more easily or make people feel unwell. This is why health experts watch them closely.

As of June 25, 2025, the World Health Organization listed some variants they are especially interested in, like JN.1, and others they are monitoring, including KP.3, KP.3.1.1, and several more. These variants help the virus continue to spread among people.

Overview

SARS-CoV-2, the virus that causes COVID-19, has changed over time through natural mutations. Scientists first noticed the virus in December 2019 and have been studying its changes ever since. Early on, there were fewer changes because there were not many infections. But as more people got sick, the virus changed more often.

Some of these changes made certain versions of the virus spread more easily. For example, the Alpha and Delta versions were found to spread faster than earlier versions. Some versions also had changes that helped them infect people even if many had already been sick or vaccinated. These special versions are watched closely by health experts around the world.

Definitions

The term variant of concern (VOC) for SARS-CoV-2, which causes COVID-19, describes a type of the virus that has changes in its spike protein. These changes can make the virus spread more easily among people.

Before a variant becomes a VOC, it might be called a variant of interest (VOI) or a variant under investigation (VUI). When fully studied, these variants are grouped into categories using systems like Pango, Nextstrain, and GISAID.

The World Health Organization updates its rules for naming these variants. It also uses terms like variants under monitoring (VUM) for variants that might be spreading more quickly in different countries.

Different groups, like the CDC in the United States, may have slightly different rules for naming these variants.

Notability criteria

Viruses change over time by picking up small differences, which can create new versions called variants. When a new variant starts to spread in a group of people, it may be called an "emerging variant". For the virus that causes COVID-19, these new versions often differ by just a few tiny pieces.

Some new variants might have special traits, such as spreading more easily or making people sicker. They might also not be caught by tests that look for the virus. If a variant shows it can cause more cases or special outbreaks, and it’s not yet widespread, it might be called a "variant of interest". If it later proves to make vaccines or treatments less effective, it could become a "variant of concern".

Nomenclature

See also: Colloquial names of SARS-CoV-2 variants

SARS-CoV-2 variants are groups of the virus that have small changes in their genetic makeup. At first, many groups and news reports named these variants after the countries where they were first found. This caused some problems, so in May 2021, the World Health Organization decided to use Greek letters like Alpha, Beta, and Gamma to name important variants. This helped people talk about them without making any country feel bad. Later, when they reached the letter Mu, they skipped Nu and Xi to avoid confusion, choosing Omicron instead. If all Greek letters are used, they might start using names of constellations.

Lineages and clades

There are many variants of SARS-CoV-2, but scientists group them into larger families called lineages or clades. Different groups have different ways to name these families:

• As of January 2021, GISAID had identified eight main groups, called clades.
• Nextstrain, a tool for tracking how viruses change, had identified 13 main groups by June 2021.
• The Phylogenetic Assignment of Named Global Outbreak Lineages (PANGOLIN) team had named 1,340 different lineages by August 2021.

Countries also have their own systems for naming variants. For example, Public Health England used to name variants by the year, month, and a number, like [2021] [01]/[01]. They have since changed this system.

National public health institutes may create their own naming systems to track variants in their area.

Reference sequence

Scientists study viruses by comparing them to a reference sample. Because we do not know when the first person got sick, the choice of reference sample can vary.

One early sample is called Wuhan-1. It was collected on December 24, 2019. Another group uses a sample collected on December 26, 2019, from the NCBI reference genome. A third sample, called WIV04/2019, was taken from a sick patient on December 30, 2019. It is often used as a reference, especially by researchers working with GISAID.

The virus first found in Wuhan, China differs from the original virus by three changes. Since then, many versions of the virus have developed.

Overview of historical variants of concern or under monitoring

The table below shows information about different versions of the virus that causes COVID-19, as known in 2021. These versions are called variants of concern. The data used to estimate risks were approximations because there wasn’t enough information for detailed studies. For four main variants — Alpha, Beta, Gamma, and Delta — tests still worked well, and some treatments remained effective. PCR tests could also detect the Omicron variant.

Previously circulating and formerly monitored variants (WHO)

The World Health Organization (WHO) says a previously circulating variant doesn't pose a major added risk to global public health compared to other circulating SARS-CoV-2 variants, but it should still be monitored.

On 15 March 2023, the WHO updated its tracking system for variants of concern, announcing that only variants of concern will be assigned Greek letters.

Previously circulating variants of concern (VOC)

The variants listed below had previously been designated as variants of concern but were replaced by other variants. As of May 2022, the WHO lists the following under "previously circulating variants of concern":

Alpha (lineage B.1.1.7)

Main article: SARS-CoV-2 Alpha variant

First detected in October 2020 during the COVID-19 pandemic in the United Kingdom, lineage B.1.1.7, labelled Alpha variant by the WHO, was previously known as the first Variant Under Investigation in December 2020 (VUI – 202012/01) and later notated as VOC-202012/01. It is also known as 20I (V1), 20I/501Y.V1 (formerly 20B/501Y.V1), or 501Y.V1. From October to December 2020, its prevalence doubled every 6.5 days. It is linked with a significant increase in the rate of COVID-19 infection in United Kingdom, partly because of the N501Y mutation. There was some evidence that this variant had increased transmissibility.

On 16 March 2022, the WHO de-escalated the Alpha variant and its subvariants to "previously circulating variants of concern".

B.1.1.7 with E484K

Variant of Concern 21FEB-02 (previously written as VOC-202102/02), described by Public Health England (PHE) as "B.1.1.7 with E484K" is of the same lineage in the Pango nomenclature system, but has an additional E484K mutation. On 4 March 2021, scientists reported B.1.1.7 with E484K mutations in the state of Oregon. Other names for this variant include B.1.1.7+E484K and B.1.1.7 Lineage with S:E484K.

Beta (lineage B.1.351)

Main article: SARS-CoV-2 Beta variant

On 18 December 2020, the 501.V2 variant, also known as 501.V2, 20H (V2), 20H/501Y.V2 (formerly 20C/501Y.V2), 501Y.V2, VOC-20DEC-02 (formerly VOC-202012/02), or lineage B.1.351, was first detected in South Africa and reported by the country's health department. It has been labelled as Beta variant by WHO.

On 16 March 2022, the WHO has de-escalated the Beta variant and its subvariants to "previously circulating variants of concern".

Gamma (lineage P.1)

Main article: SARS-CoV-2 Gamma variant

The Gamma variant or lineage P.1, termed Variant of Concern 21JAN-02 (formerly VOC-202101/02) by Public Health England, 20J (V3) or 20J/501Y.V3 by Nextstrain, or just 501Y.V3, was detected in Tokyo on 6 January 2021 by the National Institute of Infectious Diseases (NIID). It has been labelled as Gamma variant by WHO.

On 16 March 2022, the WHO has de-escalated the Gamma variant and its subvariants to "previously circulating variants of concern".

Delta (lineage B.1.617.2)

Main article: SARS-CoV-2 Delta variant

The Delta variant, also known as B.1.617.2, was a globally dominant variant that spread to at least 185 countries. It was first discovered in India. It was first discovered in October 2020 and has since spread internationally. On 6 May 2021, British scientists declared B.1.617.2 as a "variant of concern".

On 7 June 2022, the WHO has de-escalated the Delta variant and its subvariants to "previously circulating variants of concern".

Previously circulating variants of interest (VOI)

Epsilon (lineages B.1.429, B.1.427, CAL.20C)

Main article: SARS-CoV-2 Epsilon variant

The Epsilon variant or lineage B.1.429, also known as CAL.20C or CA VUI1, 21C or 20C/S:452R, is defined by five distinct mutations. From September 2020 to January 2021, it was more transmissible than earlier variants in California.

Epsilon (CAL.20C) was first observed in July 2020 by researchers at the Cedars-Sinai Medical Center, California. After an initial increase, its frequency rapidly dropped from February 2021 as it was being outcompeted by the more transmissible Alpha.

Zeta (lineage P.2)

Eta (lineage B.1.525)

Main article: SARS-CoV-2 Eta variant

The Eta variant or lineage B.1.525, also called VUI-21FEB-03 (previously VUI-202102/03) by Public Health England (PHE) and formerly known as UK1188, 21D or 20A/S:484K, does not carry the same N501Y mutation found in Alpha, Beta and Gamma, but carries the same E484K-mutation as found in the Gamma, Zeta, and Beta variants.

As of July 2021, UK experts are studying it to ascertain how much of a risk it could be.

Theta (lineage P.3)

Main article: SARS-CoV-2 Theta variant

On 18 February 2021, the Department of Health of the Philippines confirmed the detection of two mutations of COVID-19 in Central Visayas. The mutations were later named as E484K and N501Y.

As of July 2021, Theta is no longer considered a variant of interest by the WHO.

Iota (lineage B.1.526)

The proportion of USA cases represented by the Iota variant had declined sharply by the end of July 2021 as the Delta variant became dominant.

Kappa (lineage B.1.617.1)

Lambda (lineage C.37)

Mu (lineage B.1.621)

Formerly monitored variants (WHO)

The variants listed below were once listed under variants under monitoring, but were reclassified due to either no longer circulating at a significant level, not having had a significant impact on the situation, or scientific evidence of the variant not having concerning properties.

Omicron

Further information: SARS-CoV-2 Omicron variant

The Omicron variant was named a serious variant by the World Health Organization on November 26, 2021.

This variant has changes in its genetic makeup. Scientists are studying how it affects how easily the virus spreads and other factors.

Omicron was first found in November 2021 in Botswana and South Africa. Cases were also found in Hong Kong, Israel, and Europe. By early 2022, it was spreading widely in many places, including India.

As time went on, new versions of Omicron appeared. BA.2 became the main type in many countries by spring 2022.

In 2022, new versions called XBB types appeared. One of these, XBB.1.5, became the most common type in the United States by late 2022.

In July 2023, a new type called BA.2.86 was found. A version of this, called JN.1, started spreading in late 2023. By early 2024, JN.1 was the most common type worldwide.

In 2024 and 2025, even more new versions appeared, such as KP.2, KP.3, XEC, XFG, and NB.1.8.1. These continued to change and spread around the world.

Omicron variants under monitoring (WHO, 2022/2023)

In May 2022, the World Health Organization began a new way to watch closely related versions of the main Omicron variant. This happened because most of the virus samples being studied were from the Omicron family. By February 2023, this group was called "Omicron variants under monitoring."

Other notable variants

Lineage B.1.1.207 was first found in August 2020 in Nigeria. Scientists are still learning about how it spreads. It has a change called P681H, which it shares with the Alpha variant. By May 2021, it had been found in 10 countries.

Other variants like B.1.1.317 made health officials in Queensland Health add extra quarantine time for two people in Brisbane, Australia. Lineage B.1.616, found in Brittany, France in January 2021, was hard to detect with normal tests. Lineage B.1.618, first found in October 2020, spread in West Bengal, India in April 2021.

In July 2021, scientists found unusual virus strains in New York City wastewater.

The B.1.640.2 variant, also called the IHU variant, was found in October 2021 in a traveler to France from Cameroon. It infected 12 people but spread more slowly than the Omicron variant.

Between November 2023 and July 2024, a very unusual variant was found in New Jersey. It disappeared by mid-2024.

Recombinant variants

In 2022, the British government told us about some mixed versions of the SARS-CoV-2 virus. These mixed versions are called recombinant variants and have special names: XD, XE, and XF.

One of these, called XE, is a mix of two other versions, BA.1 and BA.2. By March 2022, scientists thought XE might spread a little faster than BA.2.

Incubation theory for multiple mutated variants

See also: Antigenic escape and Escape mutation

Researchers have found that in people whose bodies have trouble fighting infections, the virus can change a lot. These changes happen more when special treatments are used. This helps the virus adapt and become different in similar ways in many patients.

Notable missense mutations

There have been many changes in the SARS-CoV-2 virus that scientists call missense mutations. These changes can affect how the virus spreads or how well vaccines work.

One important change is called D614G. This change happened early in the pandemic and became common around the world. It seems to help the virus spread more easily.

Another change, N501Y, was found in several variants and may help the virus connect better to cells in our bodies. There are also changes like L452R and E484K that might make it harder for vaccines to work as well. Scientists watch these changes closely to understand how the virus might behave differently.

Data and methods

Modern DNA sequencing can help find new versions of germs quickly during sickness outbreaks. Scientists use special computer programs to group similar germ sequences together. This helps them see how the virus changes over time. By January 2021, scientists had collected more than 330,000 sequences of the virus that causes COVID-19.

Countries worked together to share their tools for studying these virus versions. One method, called wastewater surveillance, can help find the virus in water. This helps track how it spreads in a community. Testing can sometimes show if a virus version is present, but this depends on which versions are most common in an area.

Cross-species transmission

Further information: Impact of the COVID-19 pandemic on animals and List of animals that can get SARS-CoV-2

There is a risk that COVID-19 could spread from humans to animals. This could mix with other animal viruses and create new types that might be dangerous to humans. These changes might come back to affect people, especially those with weaker immune systems.

Cluster 5

Main article: Cluster 5

In November 2020, a special type of the virus called Cluster 5 was found in Northern Jutland, Denmark. It is believed to have come from minks to humans through mink farms. To stop this from spreading, Denmark decided to remove the mink population and put restrictions on travel in some areas. This was done to protect efforts to control the COVID-19 pandemic. Tests later showed that Cluster 5 was no longer spreading among people.

Vaccines

Main article: COVID-19 vaccine

During the COVID-19 pandemic, vaccines were made to help protect people from the virus. Many people got these vaccines, especially those who were most at risk.

Scientists watched to see if new versions of the virus could make the vaccines less effective. By February 2021, experts in the United States thought the vaccines still worked well against the versions of the virus that were spreading at that time.

See also: Oxford–AstraZeneca COVID-19 vaccine § Effectiveness, Pfizer–BioNTech COVID-19 vaccine § Effectiveness, Moderna COVID-19 vaccine § Effectiveness, Janssen COVID-19 vaccine § Efficacy, Novavax COVID-19 vaccine § Efficacy, Sinopharm BIBP COVID-19 vaccine § Effectiveness, Sputnik V COVID-19 vaccine § Effectiveness, CoronaVac § Effectiveness, Covaxin § Efficacy, ZF2001 § Efficacy, Abdala (vaccine) § Efficacy, SCB-2019 § Efficacy, and COVID-19 vaccine clinical research § Variants