A new strain of coronavirus in the UK has led to stricter social distancing restrictions in Britain just a week before Christmas and sent alarm bells ringing around the world.
Scientists say they have "moderate confidence" the mutation means the virus will now spread more easily, although there is no evidence the new strain is any more deadly than the previous versions.
The latest variant is not the first time the virus has mutated since it was first detected in Wuhan, China, but scientists are concerned due to the high number of potentially important alternations in the new strain, which early analysis puts at 17.
One important change related to the virus' spike protein, reports the BBC. This is key to how the virus enters our body's cells, and the change means it is easier for the virus to get inside us.
Another mutation detected appears to make antibodies from the blood of survivors less effective at attacking the virus.
British Prime Minister said the new variant may be as much as 70 percent more transmissible than previous versions. Discovery of the strain led to full lockdown restrictions being imposed in London, southeast and eastern England and Wales over the weekend.
Experts say the most likely way the virus mutated was that it emerged in a patient with a weakened immune system that was unable to beat the virus. Their body then became a "breeding ground for the virus to mutate", according to the BBC.
Following the announcement of the new strain, a number of countries banned travellers from the UK.
Will the vaccine still work?
The first question that comes to mind when people hear the virus has mutated is: will the vaccine still work?
Thankfully, the answer to this appears to be yes.
Jesse Bloom, an evolutionary biologist at the Fred Hutchinson Cancer Research Center in Seattle told the New York Times it would take years, not months, for the virus to evolve enough to make the current vaccines unable to defend against it.
"No one should worry that there is going to be a single catastrophic mutation that suddenly renders all immunity and antibodies useless," he told the Times.
"It is going to be a process that occurs over the time scale of multiple years and requires the accumulation of multiple viral mutations.
"It’s not going to be like an on-off switch."
However, Professor Ravi Gupta of the University of Cambridge told the BBC if more mutations are added to the strain "then you start worrying".
"This virus is potentially on a pathway for vaccine escape, it has taken the first couple of steps towards that," Prof Gupta said.
