Spanish scientists have identified a new trait of the COVID virus that explains how it evolves and adapts to humans: "Mutant Clouds."

An international group of scientists, led by Spanish researchers, has discovered a previously unknown characteristic of the SARS-CoV-2 virus that allows us to better understand its adaptation to the human population during the pandemic . The work reveals that, over time, the coronavirus has decreased its internal genetic diversity.

The study, published in the journal Proceedings of the National Academy of Sciences (PNAS), was conducted by experts from the Severo Ochoa Center for Molecular Biology (CBM, CSIC-UAM), the Jiménez Díaz Foundation through its Health Research Institute (IIS-FJD), the Polytechnic University of Madrid , and Northwestern University (United States).

Celia Perales, Esteban Domingo, and Ignacio Gadea led the study that shows how SARS-CoV-2, like other RNA viruses, replicates by forming what are called "mutant clouds," i.e., groups of viruses with small genetic differences between them.

However, while in the first waves of the pandemic these clouds were broad and highly diverse, in more recent variants, such as Omicron, they have become much smaller. "Our work shows that the internal diversity of the virus also evolves, and this change can influence how it is transmitted or how it responds to the immune system. Monitoring this dynamic is key to anticipating its behavior," explained Perales, a researcher at the CBM and co-lead author of the study.

Scientists emphasize that this discovery connects, for the first time, the molecular biology of thecoronavirus with its epidemiological behavior, opening up new opportunities for the development of more effective vaccines and treatments.

Evolution of the general genetic structure of the virus

Rather than focusing exclusively on specific mutations, the researchers note that it is also critical to analyze the evolution of the virus's overall genetic structure .

The study suggests that factors such as the mode of transmission, the tissues in which the virus replicates, and the immune system's response directly influence its internal diversity. This diversity, according to the researchers, has been progressively adjusted as SARS-CoV-2 has adapted to the human species.