The coronavirus which has caused a worldwide pandemic has mutated into an even more contagious strain, scientists believe.
The 'mutant' strain is sweeping Europe and the US and may even have the potential to reinfect those who already have antibodies, it is claimed.
Researchers at the Los Alamos National Laboratory in the US say 14 mutations of Covid-19 have been identified, one of which started in Europe.
The new strain reportedly spread across the continent in Europe, before spreading to the US and Canada, then across other parts of the globe by the end of March.
Authors of the 33-page report say they felt an "urgent need for an early warning" so that vaccine manufacturers around the world will be prepared to take on the more deadly mutated strain.
Scientists say that if Covid-19 doesn't subside in the summer, it could mutate and make any coronavirus vaccine ineffective.
"The story is worrying, as we see a mutated form of the virus very rapidly emerging, and over the month of March becoming the dominant pandemic form," study leader Bette Korber from Los Alamos, wrote on her Facebook page.
"When viruses with this mutation enter a population, they rapidly begin to take over the local epidemic, thus they are more transmissible."
Worryingly, the researchers believe that the new strain not only spreads faster, but may also leave people vulnerable to a second infection.
In the study, the team analysed more than 6,000 coronavirus sequences from around the world.
Delving deeper into the results, the researchers found that Italy was one of the first countries to see the new strain of the virus, in the last week of February.
And while New York was hit by the original strain around March 15, the mutant strain had taken over in a matter of days.
Ms Korber added: "We cannot afford to be blindsided as we move vaccines and antibodies into clinical testing.
“Please be encouraged by knowing the global scientific community is on this, and we are cooperating with each other in ways I have never seen … in my 30 years as a scientist."
