Variantes del coronavirus: lo que sabemos hasta ahora

Coronaviruses are RNA virus belonging to coronaviridae family. These virus display remarkably high rates of errors during replication due to lack of proofreading nuclease activity of their polymerases. In other organisms, the replication errors are corrected but the coronaviruses lack this ability. As a result, replication errors in coronaviruses remain uncorrected and accumulate which in turn act as source of variation and adaptation in these virus. Thus, it has always been nature of things for the coronaviruses to undergo mutation in their genomes at extremely high rates; more the transmission, more replication errors happen and hence more mutations in the genome leading to more variantes como consecuencia. 

Obviamente, cambiar a nuevo variantes no es nuevo para coronavirus. Humano coronavirus have been building up mutations to new forms in the recent history. There were several variantes responsible for various epidemics since 1966, when the first episode was recorded.  

The SARS-CoV was the first lethal variant that caused coronavirus epidemic in Guangdong Province of China in 2002. MERS-CoV was the next important variant that caused epidemic in Saudi Arabia in 2012.  

La novela coronavirus SARS-CoV-2, the variant responsible for the current COVID-19 pandemic that started in December 2019 in Wuhan, China and subsequently spread worldwide to become the first coronavirus pandemic in the human history, has continuously undergone further adaptation accumulating mutations in different geographical regions giving rise to several sub-variantes. These sub-variantes have minor differences in their genome and the spike proteins and show differences in their transmission rate, virulence and immune escape infectivity.  

Based on the threat that these sub-variants pose, they are grouped into three categories – variantes of concern (VOC), Variants of interest or Variants under investigation (VOI) and Variants under monitoring. This grouping of sub-variants is based on evidences related to transmissibility, immunity and severity of infection.    

1. Variantes preocupantes (VOC) 

Las variantes preocupantes (COV) tienen una clara asociación con el aumento de la transmisibilidad o virulencia o la disminución de la eficacia de cualquier medida de salud pública, como la eficacia de las vacunas que se utilizan actualmente. 

2. Variantes de interés o Variantes bajo investigación (VOI) 

Se sabe que las variantes de interés o variantes bajo investigación (VOI) tienen cambios genéticos que pueden afectar su transmisibilidad, virulencia o efectividad de las medidas de salud pública y se identifica que causan una transmisión comunitaria significativa.

3. Variantes bajo seguimiento  

Las variantes bajo supervisión se detectan como señales y hay indicios de que pueden tener propiedades similares a un COV, pero la evidencia puede ser débil. Por lo tanto, estas variantes se controlan constantemente para detectar cualquier cambio.  

Esta agrupación es dinámica, lo que significa que las subvariantes pueden eliminarse de un grupo o incluirse en cualquier grupo dependiendo del cambio en la evaluación de las amenazas en términos de transmisibilidad, inmunidad y gravedad de la infección.  

Ironically, evolution of SAR-CoV-2 currently seems to be ongoing process. Going by the nature of this virus, so long there is transmission among humans there will be replication errors and mutations. Some mutant or variant may overcome the selection pressure to become more infectious and virulent or escape immune response to make vaccine less effective. Possibly, many more variants will be detected in due course in the regions of higher transmission. Minimising transmission and constant monitoring are the key to containment strategies.  

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Fuentes:  

1. Prasad U., 2021. New Strains of SARS-CoV-2 (the virus responsible for COVID-19): Could ‘Neutralising Antibodies’ Approach be Answer to Rapid Mutation? Scientific European. Posted 23 December 2020. Available online at http://scientificeuropean.co.uk/medicine/new-strains-of-sars-cov-2-the-virus-responsible-for-covid-19-could-neutralising-antibodies-approach-be-answer-to-rapid-mutation/  

2. OMS, 2021. Seguimiento de variantes del SARS-CoV-2. Disponible en línea en https://www.who.int/en/activities/tracking-SARS-CoV-2-variants/ 

3. ECDPC 2021. Variantes preocupantes del SARS-CoV-2 al 8 de julio de 2021. Disponible en línea en https://www.ecdc.europa.eu/en/covid-19/variants-concern 

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