4 coronavirus variants can make people sicker or spread faster, including the Delta variant first found in India. Here's what variants are, and why experts are so concerned about them.
There are four coronavirus variants, including the Delta variant, that experts around the world are particularly worried about.
These variants were first identified in South Africa, the UK, Brazil, and India respectively.
Others coronavirus variants have concerning features, but it's not yet clear they're more dangerous.
Several coronavirus variants have evolved mutations that mean they spread more easily, make people sicker, escape immune responses, evade tests, or render treatments ineffective.
These are called "variants of concern" by the World Health Organization, and there are four that have spread to the US, including the Delta variant first found in India.
There are various other variants that may have troubling features, which experts are looking into. These are called "variants under investigation."
They differ from the original virus strain in a number of key ways.
Variants of concern
Alpha (B.1.1.7, first found in the UK)
Alpha was first detected in two people in south-east England. It was reported to the World Health Organization (WHO) on December 14.
It has been identified in 135 countries worldwide, including the US, where there are more than 20,000 reported cases, according to the CDC. It became the most common variant in the US on April 7. Tennessee has the highest proportion of Alpha cases of any state, accounting for 86% of sequenced cases.
Alpha is between 30% to 50% better at spreading from person to person than most other coronavirus variants, according to UK scientists. It's about 60% less infectious than the Delta variant first identified in India.
Alpha could be more deadly, but we don't know for sure
Alpha could be more deadly. The UK government's New and Emerging Respiratory Virus Threats Advisory Group (NERVTAG) reported a model on January 21 that showed someone infected with Alpha is 30% to 40% more likely to die than someone with a different variant.
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Community-based studies in England, Scotland and Denmark showed that infection with Alpha in the community causes a higher risk of severe disease requiring hospital treatment and death.
But there is a lot of uncertainty around the numbers. Two studies published in the Lancet Infectious Diseases and the Lancet Public Health on April 13 indicated that Alpha was more infectious, but didn't cause worse illness in hospitalized patients.
COVID-19 vaccines from Pfizer-BioNTech, Moderna, Johnson & Johnson and AstraZeneca all appear to protect against Alpha.
Beta (B.1.351, first identified in South Africa)
Beta was first detected in Nelson Mandela Bay, South Africa, in samples dating back to the beginning of October 2020. It was reported to the WHO on December 18.
It has been found in 92 countries, including the US, where there are 453 cases reported across 36 states and jurisdictions according to the CDC
Beta is thought to be 50% more contagious than the original strain, according to South African health officials.
It's not thought to be more deadly. But there is evidence from South Africa that when hospitals came under pressure because of the variant's spread, the risk of death increased.
Beta may evade the body's immune response
The variant may evade the body's immune response, data suggests. Antibodies work best when they attach snugly to the virus and stop it from entering our cells. Beta has mutations called E484K and K417N at the site where antibodies latch on. In early lab tests, antibodies produced by Pfizer and Moderna's COVID-19 vaccines couldn't attach as well to Beta, compared to the original coronavirus.
In a real-world Qatari study reported on May 6, Pfizer's vaccine was 75% effective at preventing infection of varying severity caused by Beta after two doses.
And another real-world study from Israel published on April 10 suggested that Pfizer's vaccine provided less protection against Beta than the original coronavirus. But it was focused on those who have already tested positive for the virus, not total infection rates, so we can't draw firm conclusions.
Johnson & Johnson's COVID-19 vaccine was 64% effective at preventing COVID-19 in trials in South Africa, where 95% infections are caused by Beta, and 72% effective in the US, where Beta accounts for less than 1% of sequenced coronavirus tests.
AstraZeneca's COVID-19 vaccine didn't prevent mild to moderate disease caused by Beta in a trial, and we don't yet know if AstraZeneca's shot still protects against severe illness caused by the variant.
It is unlikely that vaccines will become completely useless against the variant. Existing vaccines could be updated and tailored to a new variant within weeks or months, or you may require a booster shot.
Gamma (P.1, first identified in Brazil)
Gamma was first detected in four people in Japan, who had traveled from Brazil on January 2. It was identified by the National Institute of Infectious Diseases on January 6, and reported to the WHO that weekend.
It has been found in 52 countries worldwide, including the US, where there have been 497 cases in 31 states, according to the CDC
Gamma is twice as contagious as the original coronavirus - it was initially detected in Amazonas, north-west Brazil, on December 4, and by January 21, 91% of people with COVID-19 in the region were infected with P.1, according to the WHO.
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Gamma has similar E484K and K417T mutations as B.1.351, which means it can evade antibody responses.
This could be the reason Gamma reinfects people who have already caught coronavirus - a study published April 14 showed that previous coronavirus infection only offered between 54% and 79% of the protection for P.1 than for other virus strains.
Gamma's mutations could also mean that vaccines work less well.
COVID-19 vaccines from Pfizer and AstraZeneca probably work against Gamma. Moderna's hasn't been tested. Johnson & Johnson's COVID-19 vaccine was 68% effective in trials in Brazil, where the variant is the most common strain, compared with its 72% efficacy in the US, where Gamma at the time accounted for 0.1% of sequenced coronavirus tests.
Delta (B.1.617.2, first identified in India)
Delta is more infectious than the original virus - it's estimated to be about 60% more contagious than Alpha, according to UK data. This is due to mutations that improves its ability to bind to the airways and help it to escape the body's immune response. People infected with Delta also have a higher viral load than with Alpha, so they spew more virus particles out into the air, passing it onto another person more easily.
Delta remains a "variant of interest," according to the CDC.
Its mutations include:
L452R: May make the virus more infectious or it may avoid the antibody response.
P681R: May make it more infectious.
Real-world data from the UK found that both AstraZeneca's and Pfizer's vaccines were highly effective against symptomatic COVID-19 caused by Delta when two doses were given. But there's isn't enough data yet to tell exactly how well it works against severe COVID-19 requiring hospital treatment.
We don't have enough data on how well COVID-19 vaccines from Moderna or Johnson & Johnson protect against Delta.
A Public Health England briefing on June 3 said that early data suggests that it could cause more hospitalizations. But this is still being debated. Some UK-based experts said in statements on June 4 that it could be that people that got sick with the variant and needed hospital treatment weren't vaccinated - two doses of Pfizer's vaccine offers some protection against it, for example.
There have been anecdotal reports of atypical symptoms from India including hearing loss and gangrene, but there's no data to back this up currently.
Variants of interest
Epsilon (B.1.427/B.1.429, first identified in California)
Epsilon consists of two slightly different mutated forms of the virus, called B.1.427 and B.1.429. It is also called CAL.20C, using another naming system. It was first found in California in July and has now been detected across the US and elsewhere, including in Australia, Denmark, Mexico, and Taiwan, according to the Global Initiative on Sharing Avian Influenza Data (GISAID).
Epsilon is estimated to be about 20% more infectious than the original coronavirus. This is likely because of a mutation called L452R mutation, which in early lab studies was shown to help the virus infect cells.
COVID-19 vaccines haven't yet been tested against this variant specifically. But early lab experiments showed that antibodies produced by previous COVID-19 infections worked only half as well against the variant as they did with the original coronavirus strain.
The CDC considers Epsilon a "variant of concern", which means the CDC experts consider that there's enough evidence that its mutations change its behavior. It remains a "variant under investigation" according to the WHO.
Zeta (P.2, first identified in Brazil)
Zeta was first detected in Brazil in April 2020. It's a "variant of interest" because it has the E484K mutation that may mean it evades antibody responses. No sequenced coronavirus tests in the US are Zeta at the moment, according to the CDC.
Eta (B.1.525, identified in multiple countries)
Eta was detected in multiple places including the UK, Nigeria and New York in December 2020. It has the E484K mutation that may mean it evades the antibody response. Eta accounts for 0.1% of sequenced coronavirus tests in the US, according to the CDC.
Theta (P.3, first identified in the Philippines)
Theta was first detected in the Philippines in February. Theta has the E484K mutation that may mean it evades the immune response. Theta hasn't yet been detected in the US.
Iota (B.1.526, first identified in New York)
Iota was detected in New York in November 2020. It's a "variants of interest" because it has mutations that may mean it can escape antibody responses. B.1.526 accounts for less than 5% of sequenced coronavirus tests in the US, according to the CDC.
Kappa (B.1.617.1, first found in India)
Kappa was first found in India in October 2020. It may have mutations that mean it can evade tests. It accounts for less than 0.1% of sequenced coronavirus cases in the US, according to the CDC.
Human behavior can help stop them spreading
The WHO has said that everyone should double down on precautions that stop the spread of variants, such as social distancing, hand-washing, mask wearing, and avoiding crowds.
"Human behavior has a very large effect on transmission - probably much larger than any biological differences in SARS-CoV-2 variants," Paul Bieniasz, a virologist at the Howard Hughes Medical Institute, told Insider.
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