The Omicron subvariants may burn themselves out in the next couple of months and there could be another outbreak of Delta or a different coronavirus strain this summer, according to a modelling study conducted in Israel.
The finding, published last week in the journal Science of The Total Environment, suggests that while Delta wiped out the variants that preceded it, Omicron has not eliminated the deadly variant which could re-emerge.
Researchers from Ben-Gurion University of the Negev (BGU) in Israel developed sensitive arrays that can differentiate variants from each other in wastewater which continues to give indications of where the coronavirus is active, even when PCR and rapid testing of people declines.
They monitored sewage in Beer-Sheva city of Israel from December 2021 to January 2022 and noticed a "disturbing interaction" between the Omicron and Delta variants.
The researchers 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," said Professor Ariel Kushmaro from BGU in a statement.
Until now, the researchers said, whenever a new, dominant, variant appeared, it overpowered its predecessor after a short parallel period.
However, in contrast to the expected dynamics whereupon the Delta variant diminishes as Omicron variant increases, results received from wastewater detection indicated a cryptic circulation of Delta even with the increased levels of Omicron, they said.
"According to the developed model, it can be expected that the Omicron levels will decrease until eliminated, while Delta variant will maintain its cryptic circulation," the authors of the study noted.
"If this comes to pass, the mentioned cryptic circulation may result in the reemergence of a Delta morbidity wave or in the possible generation of a new threatening variant," they added.
According to the researchers, including Karin Yaniv from BGU, Omicron is spreading swiftly around the world with record morbidity reports.
Unlike the Delta variant, previously considered to be the main variant of concern in most countries, the dynamics of the Omicron variant have shown different characteristics, they said.
The researchers noted that the deployment of wastewater-based epidemiology is recommended as a convenient and representative tool for pandemic containment.