ByJUDY SIEGEL-ITZKOVICH

JUNE 13 2026 08:59

A vital phase in the development of many pandemics takes place when a virus carried by animals starts infecting people and then adapts to transmit more effectively between individuals.

Because of this researchers and physicians closely monitor viruses that might cross from animals into humans such as new forms of bird flu and bat coronaviruses as well as agents like hantavirus and Ebola that have already entered human populations yet still spread inefficiently among people.

Within only a few months the team reproduced in a laboratory vessel the evolutionary journey followed by the coronavirus throughout the COVID-19 pandemic beginning with the original Wuhan strain and culminating in the appearance of highly transmissible Omicron variants.

This accomplishment arose from a new partnership involving the laboratories of Prof. Gideon Schreiber at the Weizmann Institute of Science Dr. Jiri Zahradnik at the First Faculty of Medicine Charles University in Prague and the BIOCEV Center.

The outcomes published in Nature Communications under the heading Stringent selection drives convergence toward omicron-like SARS-CoV-2 receptor-binding motifs generate optimism that scientists may eventually anticipate viral evolutionary paths and the conditions under which fresh infection waves could arise.

Limited selection pressure produces diverse viral forms

The laboratory simulation of this process performed at Weizmann was directed by Aviv Shoshany from Schreiber team. Under limited selection pressure by contrast numerous viral forms persist and beneficial mutations become more common without fully dominating. This situation was modeled by Ruojin Tian Dr. Miguel Padilla-Blanco and Dr. Martin Mokrejs from Zahradnik group in Czechia.

Zahradnik who earlier completed postdoctoral training in Schreiber laboratory concentrated on limited selection while the Weizmann researchers emphasized stronger selection. We observed that beginning with Omicron even under limited pressure the variant stays stable and persists. We examined only a portion of a viral protein and most mutations occurred within that region.

It required only several months to reach our findings yet we devoted more than two years to preparing the manuscript for publication because numerous additional tests including mathematical modeling were necessary Schreiber recalled. It was remarkable. Billions of individuals became infected yet the outcome remained consistent we identified the core of viral evolution. Few situations match this pattern.

In August 2021 Schreiber and collaborators reported results from an in vitro evolution study that pinpointed a pair of mutations at the coronavirus binding site enabling greater contagiousness through enhanced attachment to receptors in the human respiratory system.

Roughly three months afterward the Omicron variant was first detected in South Africa and upon sequencing researchers identified the identical pair of mutations. At that point Schreiber recognized that the in vitro evolution technique created in his laboratory might forecast significant shifts during pandemics.

Schreiber who obtained his degrees at the Hebrew University of Jerusalem and pursued postdoctoral studies at Cambridge University explained to The Jerusalem Post that evolution advances via mutations and natural selection. To persist and propagate viruses multiply rapidly which frequently produces genetic mistakes that accumulate and generate new variants. In the current investigation the researchers copied the gene for the coronavirus binding site through a deliberately error-prone process thereby accelerating the emergence of mutations.

Employing genetically modified baker yeast cells they presented millions of resulting variants to human receptors and mimicking natural selection preserved only those that continued to bind effectively. By iterating cycles of mutation and selection repeatedly the scientists reconstructed the evolution of virus-human interaction across an entire pandemic period.

At the outset of this evolutionary contest conducted in a test tube stood the original Wuhan strain together with several variants that appeared during the pandemic including Alpha Beta and Omicron. The researchers examined how their binding sites changed under two conditions strong selection pressure and limited selection pressure. Strong selection pressure describes a setting in which only a few viruses endure each evolutionary step allowing advantageous mutations to swiftly become prevalent.

Regardless of the starting viral variant under strong selection pressure a form closely resembling Omicron and its sub-variants appeared promptly and quickly dominated the population Schreiber noted. The identical trajectory occurred during the coronavirus pandemic which has experienced no further major change since Omicron emerged and prevailed at the close of 2021.

Certain future pandemics that transfer from animals to humans could follow a comparable route accelerated evolution ending in dominance by a highly contagious viral form specifically adapted to attach to human receptors Schreiber forecast.

The evolutionary route leading to Omicron dominance did not appear under limited selection pressure and computer modeling clarified the reason he added. During mutation several changes can arise at once. If one mutation confers a survival benefit and enables a new variant to dominate other mutations that are neutral or even harmful can accompany it and spread as well. The modeling indicated that under strong selection pressure advantageous mutations prevail before accompanying mutations accumulate. Under limited selection pressure however beneficial mutations carry along many extra mutations thereby reducing their own dissemination benefit.

To endure within hosts the virus had to repeatedly overcome residual immune responses and continually attach to receptors in the respiratory tract Schreiber clarified. These conditions precisely match strong selection pressure and our investigation demonstrates they are required for Omicron emergence further supporting the idea that it arose in individuals with weakened immunity. Notably when selection began from Omicron both strong and limited pressures sufficed to preserve the Omicron sequences accounting for why this variant continues in the broader population. This underscores the necessity of properly managing immunosuppressive conditions such as AIDS ahead of the next global pandemic and shielding immunocompromised persons from infection and prolonged illness.

He acknowledges that today the coronavirus draws far less attention locally and internationally than four years earlier. Individuals have moved on because of newer challenges yet next time I hope we will respond more effectively to pandemics. We now possess excellent instruments to comprehend how they progress.

The in vitro evolution technique we created could be extended in the future to additional viruses of concern he notes. We will be able to isolate viral proteins and study how they are projected to evolve under varied conditions. Our method enables identification of hazardous variants before they dominate thereby directing efforts toward preventing the circumstances that permit their takeover and preparing for them in advance.