'Deltacron', a combination of the Delta and Omicron coronavirus strains, has officially been identified as a variant of its own.
The news comes as Gisaid, a global community of scientists that shares virus information, announced cases of the variant had been discovered in France, while the World Health Organization confirmed in a briefing the strain had also been found in the Netherlands and Denmark.
Concerns were raised about the existence of an Omicron-Delta combination following investigations by a lab in Cyprus earlier this year, and the variant has now been confirmed after virologists from L'Institut Pasteur in Paris sequenced its genome.
Scientists cited by Sky News have said the 'backbone' of the variant is derived from Delta, while the part of the virus that attaches itself to human cells, known as the spike, comes from Omicron. It is thought to have started circulating in early January.
Maria van Kerkhove, the COVID technical lead for the WHO, has said the mutation was 'to be expected, especially with intense circulation of Omicron and Delta'.
Combined viruses are created when a patient is infected with two variants at the same time, after which their cells replicate together. Last month, the UK Health Security Agency (UKHSA) announced a case of a person who had contracted both the Delta and Omicron variants.
Professor Lawrence Young, a virologist at the University of Warwick, told The Guardian: 'These recombinants arise when more than one variant infects and replicates in the same person, in the same cells. Deltacron is a product of both the Delta and Omicron variants circulating in the same population.'
Van Kerkhove has assured her team was 'tacking and discussing' the variant, which is also suspected of infecting a number of people in the US, along with two cases there that have been confirmed, and about 30 people in the UK, according to the UKHSA.
Scientists have expressed belief that Deltacron will not pose a danger to vaccines, and noted that the human population has already developed substantial immunity to both variants separately.
Speaking to USA Today about the discovery, Dr William Lee, chief science officer at the California lab Helix, which sequences COVID-19 samples for the Centers for Disease Control and Prevention, said: 'The fact that there is not that much of it, that even the two cases we saw were different, suggests that it's probably not going to elevate to a variant of concern level.'
The small number of Deltacron cases that have been identified so far mean there is no concrete data about the severity of the variant or how well vaccines protect against it.