A rapid rise in infections in the UK at the end of 2020 was likely to have been fuelled by a variant of coronavirus thought to have originated in Kent.
It's one of multiple variants identified in the past few months, raising concerns about the effectiveness of vaccines manufactured to target the original variant.
So how do these news versions differ from the one we've been living with for nearly a year and will the vaccine still protect us?
Here's what you need to know:
What variants have been identified in the UK and when?
September 2020 - The so-called Kent variant was first identified. Eventually blamed for the high rates of infection in the run up to Christmas which saw a last minute reversal of the relaxation of the rules.
December 2020 - The South African variant was first identified in the UK. It is now under investigation in several postcode areas of England where cases not linked to travel have been found. The discovery has led to mass door-to-door testing in these areas in a bid to control the mutation before it takes hold.
ITV Science editor Tom Clarke discusses the latest variants
January 2021 - A leading virologist warns one of the two Brazilian Covid variants has been detected in the UK.
February 2021 - Two of the most recent variants of Covid identified in the UK are homegrown - one first identified in Bristol, the other in Liverpool.
The Bristol variant has been designated a "Variant of Concern", by the New and Emerging Respiratory Virus Threats Advisory Group (NERVTAG).
While the Liverpool one has been designated as a "Variant under Investigation" by the group.
A variant known only as 'B.1.525' was also discovered in the UK in February. It has genetic similarities to the Brazilian and South African variants.
These are just some of the 4,000 variants that have been identified around the world and scientists are continuing to monitor mutations and their possible impact on vaccine efficiency.
How many times has Covid mutated - and why should we be concerned?
All viruses mutate and the SARS-Cov-2 is no exception.
There have been many genetic variants of Covid-19 identified since the disease was first understood.
Mutations are more likely the more infections there are as the virus is under renewed pressure to evolve, as so many millions of people have now become infected.
Whilst most mutations are no cause for concern, some mutations mean that the evolution of the virus can mean it is more transmissible or harmful.
How do the new variants differ from the original strain?
The UK variant has 23 different characteristics to the original Covid-19 virus, many of them specifically linked to the proteins.
It is thought to be up to 70% more transmissible than the original and is now the dominant strain of the virus in the UK.
The new fast-spreading variant of Covid-19 in the UK is thought to be more deadly than the original strain of the virus.
The UK's chief scientific advisor Sir Patrick Vallance has said there is early evidence suggested the new UK variant could increase mortality by almost a third in men in their 60s.
ITV News' Science Editor Tom Clarke said: "The South Africa strain shares one mutation with the UK strain called 501Y: a potentially crucial one on the bit of the virus’s 'receptor binding domain' that might help it grab onto our cells and infect them.
"But it has several other potentially important mutations that are completely different from the ones the UK strain has evolved."
This mutation is also shared by the strain identified in Brazil.
Professor Ravi Gupta, Professor of Microbiology at the University of Cambridge, said: "The Brazilian variant has three key mutations in the spike receptor binding domain (RBD) that largely mirror some of the mutations we are worried about it in the South African variant, hence the concern."
There are now at least 170 known infections of the South African variant in the UK, but figures are lagging and experts warned it was “very possible” it is already quite widespread in the UK.
Door-to-door testing is now underway in several parts of the country where the strain has been identified.
An E484K mutation that is worrying scientists is also being investigated by Public Health England (PHE) in the UK.
Some 76 cases of the two new strains - Bristol and Liverpool - have been found so far in the UK.
The E484K mutation has been shown to reduce the effectiveness of vaccines in preventing people contracting Covid-19.
Are there any differences in symptoms between the variants?
People with the new Kent variant of coronavirus are less likely to report a loss of taste and smell, according to the Office for National Statistics (ONS).
They are more likely to report “classic” symptoms of the virus, such as a cough and a fever.
Sore throats and muscle pain were significantly more likely to be reported by people infected with the new variant.
It is not yet clear whether there are differences in symptoms with the Brazil and South Africa variants as the study only compared the UK variant with the original coronavirus strain.
Will the vaccines work against the new variants?
There is evidence that existing vaccines will work against the UK variant, but a study has suggested the Oxford/AstraZeneca was not effective against mild illness caused by the South African variant.
On Sunday, lead researcher in the Oxford team Professor Sarah Gilbert said the current vaccines “have a reduction in efficacy against some of the variant viruses”.
However, she added: “What that is looking like is that we may not be reducing the total number of cases but there’s still protection in that case against deaths, hospitalisations and severe disease.”
But The Pfizer/BioNTech Covid-19 vaccine has been found - albeit in a very small study - be effective against the coronavirus variant.In a US study of 20 vaccine recipients, researchers at the University of Texas Medical Branch at Galveston found that the vaccine neutralises the virus with the N501Y and E484K mutation.
The Johnson and Johnson vaccine was found to be 57% effective against moderate to severe Covid-19 in South Africa.
Prof Gilbert said her team currently has “a version with the South African spike sequence in the works” with the hopes it will be ready to administer by the autumn.
Watch this ITV News graphic showing the difference between the UK variant and those found in South Africa and Brazil:
What is the government doing to curb the spread of other variants in the UK?
The government has introduced stricter quarantine rules in a bid to curb the risk of new variants being brought to the UK.
UK nationals and residents returning to Britain from "red list" countries will be forced to quarantine for 10 days in government-provided accommodation.
In addition, anyone arriving in the UK from any country will need to take two Covid tests before being allowed to leave isolation, whether they are quarantining at home or a hotel.
Ten year jail terms are among a range of new punishments being brought in to improve compliance with these border controls.
Scientists have also urged the government not to ease lockdown rules due to evidence that the UK variant may be more deadly.