A new study entitled "The chaos law is a principal driver of natural selection: A proposition on the evolution of recently emerged coronaviruses" has been published in the scientific journal PLOS ONE.

The research, conducted by Giorgio Palù, President of the Italian Medicines Agency, Pier Francesco Roggero and Arianna Calistri of the Department of Molecular Medicine of the University of Padua, applies the chaos theory to explain the evolution of SARS-CoV-2, causative agent of the recent COVID-19 pandemic, and compare it with that of other coronaviruses that have recently affected humans (Coronavirus SARS-CoV-1 and MERS-CoV) and Ebolavirus, proposing a new perspective on the evolution of emerging viruses.

Chaos theory has rapidly progressed as a branch of mathematics and asserts that within the apparent randomness of complex natural systems there are precise underlying patterns that are able to explain the variations occurring in the systems themselves, almost assuming a predetermined evolutionary path.

“The discovery that the law of chaos also applies to viruses has obvious public health implications in terms of controlling future epidemic-pandemic emergencies,' says Giorgio Palù. It can also help broaden perspectives on genetic evolution and systems biology related to the study of viruses, microbial populations and ecosystems that impact on human life and the planet”.

The article addresses the concept of chaos and how it can influence the evolution of viruses in populations. The reproductive capacity measured for the different variants of SARS-CoV-2 (from the Wuhan prototype to Omicron) shows that the evolution of the virus does not depend on chance but on chaotic growth in its initial expansion phase (Wuhan-Alpha) linked to the initial genetic characteristics of the virus. During adaptation to humans, moreover, a small number of mutations on a 30,000-base genome, with many mutations identical for all variants, is able to alter the contagiousness and lethality of the coronavirus. This seems to be evidence that mutations converge towards an attractor, which in this case would be the initially more favourable mutations that become 'fixed' mutations and are specific for the greater adaptability and survival of the coronavirus in humans. If mutations depended on chance then they would no longer be 'fixed' mutations and the probability of them appearing in all variants would be virtually zero.

“It should be emphasised that the chaotic growth is only evident in the initial phase of the SARS-CoV-2 pandemic expansion – underlines Giorgio Palù. The fact that other highly diffusive and lethal but non-pandemic viruses such as the SARS-CoV-1 and MERS-CoV coronaviruses and the Ebolavirus do not have this behaviour suggests that an initial chaotic growth is the necessary pre-requisite that guarantees an emerging virus the intrinsic ability to become pandemic”.