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What lies ahead for SARS-CoV-2 variants?

The majority of mutations in the coronavirus that causes severe acute respiratory syndrome (SARS-CoV-2) produce only minor harm. A modest number of alterations, on the other hand, can increase viral pathogenicity and strengthen host-virus interactions, both of which are necessary for viral entrance and infection. Because the spike protein promotes viral attachment to host cell surface receptors, changes in the SARS-CoV-2 spike protein can have a profound impact on viral behavior.

To avoid the formation of new SARS-CoV-2 variations that are resistant to currently existing vaccinations and treatments, it is critical to monitor and limit virus circulation. Despite the efforts of several governments throughout the world, mass vaccination campaigns have not attained the population coverage essential to prevent SARS-CoV-2 transmission,

SARS-CoV-2 variants
Image Credit: Naeblys / Shutterstock.com

SARS-CoV-2 variant classification

It is critical to examine the emergence and spread of variations, as well as their effects on disease transmission and human health, in order to effectively control the pandemic. SARS-CoV-2 variations with a potential public health risk have been divided into three groups by the World Health Organization (WHO): variants under monitoring (VUMs), variants of interest (VOIs), and variants of concern (VOCs).

VUMs are viral variations having genetic alterations that change viral properties, but their phenotypic or epidemiological significance is unknown. Mutations in VOIs can influence infectivity, disease progression, and diagnostic or therapeutic escape, potentially resulting in community transmission and a global public health issue. VOCs have been linked to higher transmissibility, virulence, or disease severity, as well as the ability to reduce the efficacy of interventions, diagnostics, therapies, and vaccinations.

Because the virus is constantly evolving, these varieties may need to be categorized in the future. Quantifying the number of variations that could constitute a public health risk is essential for future planning in the battle against viral outbreaks.

About the study

Researchers used a function that solely rely on the global number of infected cases since the start of the pandemic to fit data on the most important SARS-CoV-2 variants according to the WHO in a new study published on the preprint platform medRxiv*. Their match allows for a fairly accurate estimate of the number of SARS-CoV-2 variants that could emerge for a given number of infected people around the world. In every epidemiological circumstance, our novel technique can also anticipate the amount of new relevant variations per 10 million instances.

The researchers gathered data on SARS-CoV-2 variants, including WHO-reported variant characteristics, PANGO (Phylogenetic Assignment of Named Global Outbreak) classification, current relevance (VOC, VOI, or VUM), date and country of first detection, total number of global cases at the end of the month of detection, and a cumulative number of variants. PANGO is a nomenclature method for recognizing and tracking SARS-CoV-2 genomic lineages. The WHO data was numerically fit using the function v(N) = k x Nlog N, where k is the numerical fit constant and is equal to 3.35 x 10−6.

“Our method depends critically on the WHO efficiency in tracking the most relevant SARS-CoV-2 variants.”

Study findings

According to the study’s findings, there were almost 44 SARS-CoV-2 subtypes that were relevant until November 2021. In November 2021, the number of new relevant variants per ten million cases was 1.64, decreasing 28.4 percent from 2.29 in March 2020.

Cumulative number of relevant SARS-CoV-2 variants
Cumulative number of relevant SARS-CoV-2 variants versus the cumulative number of cases in the world. The dots from 1 to 10 indicate the data reported by WHO [12] from March 2020 to May 2021; the solid line represents the numerical fit υ = k · N/log N obtained with Wolfram Mathematica

Until November 2021, there were around 252 million COVID-19 instances worldwide, which corresponded to 43.7 relevant variants. This is nearly 19 variations more than what the WHO published in May 2021.

Conclusions

The number of new significant variations per ten million instances fell relatively slowly as the total number of cases increased, according to the findings of this study. As a result, new SARS-CoV-2 variations will continue to evolve as long as the virus is in circulation.

Using the cumulative global number of infected cases, the scientists developed a mathematical model to calculate the number of relevant SARS-CoV-2 variants. This model simply looked at the relationship between the number of virus replications and the appearance of important variants, ignoring all other parameters that affect the spread of new variants.

The capacity to anticipate the frequency of new relevant SARS-CoV-2 variations will be critical in the future for effective vaccination campaign planning, as novel variants can change viral properties and have a significant impact on global pandemic management.

*Important notice

Preliminary scientific papers published on medRxiv are not peer-reviewed and should not be regarded as conclusive, should not be used to influence clinical practice or health-related behavior, and should not be recognized as established information.

Journal reference:

Littera, R., & Melis, M. (2021). How many relevant SARS-CoV-2 variants might we expect in the future? medRixv.

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