The government has announced today that "surge testing" will take place in various parts of the UK after the South Africa variant of the coronavirus was detected there.
Everyone in these areas over the age of 16 will be "strongly encouraged" to take a COVID test this week, after cases were found that could not easily be linked to those who had travelled to South Africa.
Here, Sky News will answer your questions about the South African variant, and how it works.
What is the new variant?
This variant could be described as similar to the Kent variant plus a bit more - as it has the same mutation as the one found in southeast England, as well as two others.
It is not uncommon for viruses to mutate similarly, and the fact that these two variants have some of the same mutations does not mean they spread from a single point, said Dr Simon Clarke, an associate professor in cellular microbiology at the University of Reading.
In fact, some of these shared mutations are also found in a variant observed in Brazil - again this likely developed separately.
Mutation is something that happens to viruses, and is not unexpected.
And it is thanks to the effectiveness of the UK's genomic research that these mutations have been found.
Dr Alison Barnett, regional director at Public Health England, said: "The UK has one of the best genomic systems in the world which has allowed us to detect the variant originating in South Africa here in Surrey."
Where in the UK is being asked to test?
So far the government has said testing for the South Africa variant will take place in the following areas:
London - W7 (Ealing), N17 (Haringey) and CR4 (Croydon)
West Midlands - WS2 (Walsall)
East of England - EN10 (Broxbourne)
South East - ME15 (Maidstone) and GU21 (Guildford)
North West - PR9 (Preston)
These are areas where cases of the virus have been discovered with no link to travel to South Africa.
So far, the government says they have identified 105 cases of the South Africa variant, 11 of which cannot be traced to travel from South Africa.
Everyone who has it has been told to self-isolate, as have their contacts.
The fact that there are untraceable cases of this disease means that the spread of infection has not been tracked fully.
Dr Clarke said that this could be down to something as simple as transmissions in the supermarket that can be difficult to follow.
Speaking at a Downing Street press conference, Dr Susan Hopkins, chief medical adviser for NHS Test and Trace, said there was no suggestion the instances of the South African variant were linked.
She added that asymptomatic carriers could have contributed to the cases.
Is this variant more dangerous or transmissible?
As the South Africa variant shares the same mutation believed to be responsible for increased transmissibility in the Kent variant, it will follow that it shares traits with it.
This includes being up to 70% more transmissible - and potentially even linked to higher mortality rates.
There are also the other two mutations on the virus.
One of these has been found to have some effect on the efficacy of antibodies stimulated by the vaccines.
Professor Jonathan Ball, professor of molecular virology at the University of Nottingham, said: "We know that some coronavirus variants might be less easily killed by antibodies raised against some of the existing vaccines, but the levels of immunity are hopefully still sufficient to prevent serious disease."
Then there is the case of the third mutation.
Not much is known about how this mutation affects the virus and people who have it.
This is something that will need to be studied and researched in order to understand what happens.
Do the vaccines work?
It is unclear at the moment exactly how well the vaccines work against this new strain, but there are some indications that this variant may be more resistant to the body's immune response.
As Dr Clarke says, this is to do with the spike protein - the bit of the virus that allows it to enter cells, like a key unlocking a door.
A vaccine trains the body to block this key with antibodies, preventing the virus from entering into people's cells.
However, one of the mutations on the South African variant seems to work against these antibodies - and so allows the virus a way back into the cells.
It is important to note that this is not the only way vaccines work - and that there are other ways they prepare the body to battle the virus.
This includes marking the spike proteins to allow the immune system to quickly identify the virus and destroy it.
Dr Hopkins said: "What we do know is that [the variant] has more mutations… that is causing perhaps to have diminished effectiveness to a vaccine but still very good."
Trials carried out by companies behind some of the the more recently researched vaccines - such as Novavax and Johnson & Johnson - showed that the jabs were around 20% to 30% less efficacious against the virus in South Africa compared with areas like the UK or US.
However, the vaccinations still reduced the severity of symptoms and helped protect people, and it has been stressed that getting the jabs is still important.