A new coronavirus strain that combines parts of the Delta and Omicron mutations has been identified, with scientists watching closely to see how contagious it might be.
The hybrid version, called “Deltacron”, has been confirmed in at least 17 patients in the US and Europe, researchers said.
Maria van Kerkhove, the World Health Organisation’s Covid-19 technical lead, said this mutation was “to be expected, especially with intense circulation of Omicron and Delta”.
She said her team was “tracking and discussing” the variant.
Virologists at the Pasteur Institute in Paris have sequenced the genome of what they called a "genuine" mixture of the strains and thus deserving of the distinction, Deltacron.
The strain has also been reported in the Netherlands and Denmark.
But because there have been so few confirmed cases, it is too soon to know whether Deltacron will be more transmissible or cause severe disease, said Philippe Colson of IHU Mediterranee Infection in Marseille, France.
Dr Colson is the lead author of a recent report on Deltacron published on medRxiv, a site that distributes complete but unpublished manuscripts.
His team described three patients in France infected with a version of Sars-CoV-2 that combines the spike protein from the Omicron variant with the “body” of the Delta variant.
The team's report has yet to be peer reviewed.
Another two unrelated Deltacron infections have been identified in the US, said a report published on medRxiv by genetics research company Helix.
On virus research bulletin boards, other teams have reported an additional 12 Deltacron infections in Europe since January — with all samples featuring an Omicron spike and a Delta body.
Genetic recombinations of coronaviruses have been known to happen when two variants infect the same host cell.
“During the Sars-CoV-2 pandemic, two or more variants have co-circulated during same periods of time and in same geographical areas … created opportunities for recombination between these two variants,” said Dr Colson.
He added that his team has designed a PCR test that “can quickly test positive samples for the presence of this … virus”.
