The Omicron variants may burn themselves out in the next couple of months and the Delta variant might re-emerge, researchers claim.

While Delta wiped out the variants that preceded it, Omicron has not eliminated Delta, said researchers from the Ben-Gurion University of the Negev in Israel. After the original SARS-CoV-2 virus that first spilt into humans around more than two years ago, several variants followed: Alpha (first detected in the UK); Beta (first detected in South Africa); Gamma (first detected in Brazil); Delta (first detected in India).

Last November, South African researchers detected the highly contagious Omicron variant, which has developed a variety of sub-variants that are currently spread all over the world. The continued circulation of SARS-CoV-2 resulted "in mutations and the emergence of various variants. Until now, whenever a new, dominant, variant appeared, it overpowered its predecessor after a short parallel period", the team wrote in the paper published in the peer-reviewed journal Science of the Total Environment.

Unlike the Delta variant, previously considered to be the main variant of concern in most countries, the dynamics of the Omicron variant showed different characteristics, they said. To understand, the team developed sensitive arrays that can differentiate variants from each other in wastewater.

Wastewater continues to give indications of where the coronavirus is active, even when PCR and rapid testing of people declines. They monitored Beer-Sheva's sewage from December 2021 to January 2022 and noticed this disturbing interaction between the Omicron and Delta variants.

They also built a model, which predicts that Omicron is burning itself out while Delta is just biding its time. "Of course, there are a lot of factors involved, but our model indicates there could be another outbreak of Delta or another coronavirus variant this summer," warned Prof. Ariel Kushmaro at BGU.

According to the model, it can be expected that the Omicron levels will decrease until eliminated, while the Delta variant will maintain its cryptic circulation. If this comes to pass, it "may result in the reemergence of a Delta morbidity wave or the possible generation of a new threatening variant", the researchers wrote.