‘Deltacron’: New Covid variant or laboratory error?

A scientist who reported the existence of a new Covid variant that combines characteristics of Delta and Omicron has insisted his findings are accurate after experts dismissed them as the result of laboratory samples becoming contaminated.

Dr Leonidos Kostrikis, a professor of biological sciences at the University of Cyprus, told the Cypriot channel Sigma TV that he and his colleagues have identified 25 cases of the so-called “Deltacron” variant, which has resulted in hospitalisation in 11 cases, and have submitted their data to the GISAID global database.

The announcement caused concern over the weekend after it trended on social media, prompting several experts to reject Dr Kostrikis’s claims.

“Deltacron is not real and is likely due to sequencing artefact (lab contamination of Omicron sequence fragments in a Delta specimen),” tweeted Dr Krutika Kuppalli, an infectious diseases researcher with the World Health Organisation.

“Let’s not merge names of infectious diseases and leave it to celebrity couples.”

Also responding to the scare was Dr Tom Peacock of Imperial College London.

“The Cypriot ‘Deltacron’ sequences reported by several large media outlets look to be quite clearly contamination - they do not cluster on a phylogenetic tree and have a whole Artic primer sequencing amplicon of Omicron in an otherwise Delta backbone,” the virologist tweeted.

“Delta sequences with strange mutations in amplicon 72 have been turning up for ages (for example Delta + Mu NTD insertion) however, they always show this non-monophyletic pattern and are nearly always more easily explained by this primer issue exacerbating very low-level contam.”

Dr Boghuma Kabisen Titanji, a global health expert, also tweeted that Deltacron was most likely the result of sample contamination, but did add: “With transmission levels of SARSCoV2 at all time highs globally, it is likely that recombination is occurring and may rise to levels that we start picking up these events more frequently. Will this lead to more concerning variants? That is possible but nobody knows.”

She continued: “The best thing we can do besides worrying about it and coining variant names that sound like a Transformers villain, is ensuring that vaccines are available to everyone and combining vaccination with other strategies that give the virus fewer opportunities to spread.”

However, Dr Kostrikis has since doubled-down on his stance, telling Bloomberg in a statement on Sunday that the cases he has identified “indicate an evolutionary pressure to an ancestral strain to acquire these mutations and not a result of a single recombination event”.

He said his team arrived at their findings after the samples were processed in multiple sequencing procedures in more than one country and that at least one sequence from Israel exhibits the genetic characteristics of Deltacron.

Dr Kostrikis added that Deltacron infection is higher among patients hospitalised for Covid-19 than among non-hospitalised patients, which would rule out the contamination hypothesis.

“These findings refute the undocumented statements that Deltacron is a result of a technical error,” he insisted.