Is the new 'Deltacron' coronavirus variant real or mere 'contamination'? What scientists say

The discovery of 25 cases of a new coronavirus variant that combines features of both Delta and Omicron has sparked a debate in the scientific community. The variant has unofficially been dubbed 'Deltacron', with a professor involved in its discovery telling Bloomberg that a high proportion of the variant has been found in patients hospitalised for COVID-19. However, several well-known scientists questioned the veracity of the claim, stating that the variant could be co-infection or the result of accidental contamination from a testing laboratory. 

The discovery was made by Leondios Kostrikis, professor of biological sciences at the University of Cyprus and head of the Laboratory of Biotechnology and Molecular Virology. “There are currently Omicron and Delta co-infections and we found this strain that is a combination of these two,” Kostrikis said, reported Bloomberg, adding that the discovery was named 'Deltacron' due to the identification of Omicron-like genetic signatures within the Delta genomes.

However, several scientists raised questions on the reports. Virologist Tom Peacock wrote on Twitter that it was more possible that Deltacron was caused by contamination or co-infection, and that there were no real indications that anything nasty was happening. "Lots of reports of Omicron sequences carrying Delta-like mutations [eg P681R or L452R]. Although a subset of these might end up being real, the vast majority will most likely turn out to be contamination or coinfection. No clear signals of anything real or nasty happening [yet]," Peacock wrote.

He later updated that the Deltacron sequences look to be quite clearly contamination, as they do not cluster on a phylogenetic tree and have a "whole Artic primer sequencing amplicon of Omicron in an otherwise Delta backbone".

How would contamination happen? One likely scenario is when testing equipment in a lab retains traces of variant A (maybe because of improper cleaning), and is then exposed to variant B, leading to wrong results. Tweeted Peacock: "New variants [coming] through sequencing lab contamination isn't that uncommon. Very, very tiny volumes of liquid can cause this."

Prominent physician Eric Topol tweeted: "Deltacron is a scariant. One less thing to worry about."

Kostrikis, however, refuted allegations that the Deltacron discovery was a technical error, telling Bloomberg that the cases he has chronicled "indicate an evolutionary pressure to an ancestral strain to acquire these mutations and not a result of a single recombination event".