While the flu spreads evenly each winter, Covid-19 is different. This also applies to the emergence and sudden spread of SARS-CoV-2 variants.
A team of German-American scientists has now shown that ‘super-spreading’ events in particular play a crucial role. So mask-wearing, hygiene and other measures remain important.
Mutations plus ‘super proliferation’
Scientists from the German Cancer Research Center (DKFZ/Heidelberg) and from the Institute of Applied Biomedical Sciences (San Diego/California) examined the emergence of SARS-CoV-2 variants in the US population based on data from the USA-SARS-CoV sequence database. -2. Thus, the combination of mutations as well as ‘super-prevalent events’ fuels the prevalence of genetic variants of viruses in the population.
Researchers identify 14 different variables
The researchers analyzed genome data for more than 62,000 SARS-CoV-2 isolates from 42 US states between January 2020 and April 2021. As early as March 2020, the team documented the first genetic aberrations from the original “Wuhan variant”, which started in no longer possible. Discovery of early summer 2020. The number of mutations per virus genome has gradually increased over time. Using specific key mutations, the researchers identified 14 different variants, some of which were distributed differently in the US states.
In the summer of 2020, researchers observed a surprisingly strong accumulation of mutations. “We suspect that a series of events called ‘super-prevalence’ caused these clusters. As a result, the rare mutations, which initially only occur in less than one percent of all infected people, can spread rapidly,” said Nina Papavasiliou. DKFZ was cited in one broadcast.
A single “ultra-experimental event” is sufficient
In the last quarter of 2020, a large number of new mutations appeared in the spiky protein gene. These 20 or so mutations were not classified as problematic and in some cases were so rare that it was in fact expected that they would be lost again. Instead, the frequency of most of these mutations increased to significant levels. “All of these mutations spread through the population,” Papavasiliou warned. “We have to realize that an additional ‘super-spreading’ event could be enough for them to spread far and wide and create new taxa.”
At the end of 2020, B.1.1.7, initially referred to as the British variant, was the first “variable of anxiety” among the US population. The genetic diversity of viruses has increased by leaps and bounds. Researchers were shocked to discover that such alarming types of viruses accumulated mutations again in just three months. Initially, widespread use of the “British variant” kept other SARS-CoV-2 mutations in check. Then the now dominant delta variant of Covid-19 pathogens evolved.
The SARS-CoV-2 genome was considered fairly stable at the start of the epidemic. But this should only apply to a limited extent. Based on careful analysis of mutation patterns, the scientists were able to identify a mechanism that could be a driver of genetic diversity: enzymes of the APOBEC group (proteinase B enzymes, which modify mRNA; note) belong to the innate defense of mammals and humans against infections. They attack the viral genome and thus can render the pathogen harmless. But this, in turn, is a selection pressure that fuels the emergence of new mutations.
“The evolution of SARS-CoV-2 will continue.”
“The SARS-CoV-2 virus will continue to evolve. Mutations are constantly occurring, and ‘superspreader events’ help them penetrate. Especially indoors and in areas with low vaccination protection,” he summarized (Plos One 2021, DOI: https://doi.org /10.1371/journal.pone.0255169). It was assumed for some time that 20 percent of infected people are responsible for 80 percent of infections.
According to scientists, without SARS-CoV-2 vaccines with full immunization (all necessary vaccine doses) in the United States due to the delta variant, there would have been a risk of catastrophe in the recent past. You should strengthen vaccination protection. In addition, vaccines with a broader effect should be developed. Especially this coming fall, wearing masks indoors, avoiding mass events and social distancing will be of great importance again.
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