Thursday, March 30

Omicron mutations already existed in infected patients many months before becoming the dominant variant

Omicron mutations already existed in infected patients months before becoming dominant, according to a study that used an ultra-deep sequencing technique that makes it possible to detect viral sequences not detectable by standard methods.

Portrait of ómicron, the variant that has marked a before and after in the pandemic

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This has been confirmed by researchers from the Higher Council for Scientific Research (CSIC) and the Jiménez Díaz Foundation. The results are published in the “Journal of Clinical Investigation”. The work has analyzed in detail samples of nasopharyngeal swabs corresponding to patients vaccinated and subsequently infected during the third wave of the pandemic in Spain.

This study has been possible thanks to the previous work on fine-tuning a powerful ultra-deep sequencing methodology that allows detecting mutated viral sequences that are found in very low proportions, which are not detectable by the usual shallow sequencing techniques.

“From each sample analyzed and from each piece of the virus analyzed, we obtain many thousands of sequences, which allows us to detect mutations at different levels of frequency coexisting within the infected patient,” explains Celia Perales, a researcher at the National Center for Biotechnology (CNB-CSIC). ) and the Jiménez Díaz Foundation Health Research Institute.

The results have revealed that despite the fact that the patients were infected with the alpha variant, predominant on that date (between January and March 2021), changes corresponding to the delta plus, iota and omicron variants were already present in those samples months before. to acquire epidemiological relevance.

“This work highlights the need to analyze virus populations with high resolution and in depth to obtain a joint view of the many mutants that coexist in each infected individual,” says Esteban Domingo, a researcher at the Severo Ochoa Molecular Biology Center. (CBMSO-CSIC-UAM).

The analyzes could allow the monitoring of mutations or a set of potentially relevant mutations before they can be part of dangerous variants, clarifies a CSIC statement. Two of the authors of this work, Celia Perales and Esteban Domingo, belong to the Network Biomedical Research Center for liver and digestive diseases, of the Carlos III Health Institute. Thanks to this, the concepts on the variability of the hepatitis C virus that they have been developing for years can now be applied to the virus that causes covid-19, according to the CSIC.