The UK said on Friday that it had identified six cases of a new coronavirus variant known as Lambda, which was first identified in Peru.
Also known as the C.37 strain, the mutation has been designated as a "variant under investigation" by UK health officials.
This is a step below the status of a "variant of concern", which is assigned to strains with more evidence of worrying mutations.
These include the Delta variant, which is fuelling a surge in UK infections and is also gaining ground in mainland Europe.
A briefing by Public Health England said Lambda’s mutations suggested potentially increased transmissibility compared with other strains.
However, evidence is limited and there is no sign that the variant causes more severe disease or is more resistant to vaccines.
Lambda is on the rise in South American countries. In Peru it accounts for 81 per cent of sequenced coronavirus cases since April.
In Chile, Lambda appeared to be overtaking the Alpha strain first identified in the UK, the World Health Organisation said.
In Argentina, cases of the variant have been growing since February.
The WHO declared the mutation to be a variant of interest on June 14 and gave it the name Lambda under its new naming system for Covid types.
Of the 1,845 Lambda samples submitted to a global database, more than half are from either Chile, Peru or the US.
Cases from the C.37 lineage have been identified in European countries including Germany, France, and Spain.
The cases in the UK – four in London, one in south-west England and one in the West Midlands – are linked to overseas travel. No deaths were reported.
The UK government said it would take “all appropriate public health interventions” against the variant, including extra testing and contact tracing.
Delta growth continues
The Delta strain now accounts for about 95 per cent of cases that are sequenced by genomic experts in the UK.
PHE’s weekly update said cases of the variant had risen by 46 per cent in the past week, to a total of more than 110,000.
There were 42 new cases of the Delta AY.1 sub-type, also known as Delta Plus.
An additional 514 people were taken to hospital with the Delta variant, of whom 304 were unvaccinated.
Dr Jenny Harries, the head of the UK’s Health Security Agency, said the data on vaccine effectiveness was encouraging.
“Through the success of our vaccination programme, data suggest we have begun to break the link between cases and hospitalisations,” she said.
“This is hugely encouraging news, but we cannot become complacent.”
Delta is also on the increase in parts of Europe, including France and Germany, and health officials believe it is likely to become dominant.
France will step up testing and vaccination in the south-western department of Landes, where the variant accounts for 70 per cent of new cases.
Across France, Delta now accounts for about 10 per cent of new cases, up from an estimated 2 per cent to 4 per cent last week.
In Germany, where Delta accounts for 15 per cent of new cases, Chancellor Angela Merkel said that Europe is “on thin ice” in its battle against the virus.
Ms Merkel called on the EU to be cautious about admitting travellers from countries with high rates of the Delta variant, which would include the UK.
She said she would like European countries to require British travellers to go into quarantine, as is the case in Germany.