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B.1.617.2 transmits even more easily and quickly than B.1.1.7. Because it is so contagious, one expert calls it a superspreader variant. This is probably due to a combination of mutations. A study shows under which circumstances there is a particularly high risk of infection.
40 to 60 percent more contagious
In the United Kingdom, the delta variant already accounts for more than 90 percent of new infections. According to a study by the British health authority, it could be 60 percent more infectious than the alpha variant B.1.1.7, which is currently still predominant in Germany. This was the result of a comparison of the frequency of infections in households. The British government currently assumes a higher overall transmissibility of 40 to 60 percent.
The fact that the delta variant is so much more contagious is probably due to a combination of mutations in the stinging protein that the virus uses to dock onto human cells. Scientists at the German Primate Center in Göttingen have analyzed them and published the results in a preprint.
Mutations inhibit antibodies
Two crucial mutations (L452R and E484Q) are located in the receptor binding domain of the protein, which is the main target of neutralizing antibodies. The scientists found that these changes, on the one hand, somewhat facilitate the penetration into cells and, on the other hand, slightly inhibit the effect of antibodies formed by vaccination or previous Sars-CoV-2 infections. This contributes to the faster spread of this variant, write the Göttingen researchers. Scientists at Cambridge University came to a similar conclusion.
Researchers at Imperial College London write in a preprint that a third mutation (P681R) facilitates the delta variant’s entry at the so-called furin cleavage site after it has docked with cells. The scientists suspect that people become infected more quickly when the virus can more easily attack cells in the respiratory tract.
Higher viral load
Co-author Wendy Braclay says the data suggest the virus “is fitter in human respiratory cells,” meaning an increased viral load in infected individuals, causing them to shed more virus into the air. Test data showed that the CT value appears to be lower in samples from delta-infected individuals, she says. In PCR testing, this value indicates the number of cycles needed to detect Sars-CoV-2. Lower values mean higher viral loads.
World Medical Association President Frank Ulrich Montgomery says, “The tricky thing with this variant is that infected people can very quickly have a very high viral load in their throat and thus infect others before they even realize they’re infected.”
This basically means that people become superspreaders more easily, and outbreaks can occur correspondingly more frequently, with one person infecting many others in a short period of time. Renowned U.S. virologist Eric Topol therefore calls B.1.617.2 a “superspreader variant.”
End of mandatory masks not a good idea
This means above all that the risk of infection by aerosols indoors is even higher with the delta variant than with the previous variants. Accordingly, one must act more cautiously and keep an eye on the growing threat from B.1.617.2. This is especially true in the fall, when infections will increase again due to the seasonality of the virus and will then be dominated by the new variant. With this in mind, an end to mandatory indoor masking is clearly not appropriate.
What to look out for in preparation can be gleaned from a recent French study that analyzed which factors increase the risk of infection on the basis of Covid 19 cases last October and November. It is important to keep in mind, however, that the details may be correlations, so there does not have to be a direct cause-and-effect relationship.
Concern about delta variant grows
According to the study, the risk of infection increases with each person living in the household as well as with children who go to school or are cared for in a daycare center. Elementary schools are an exception, according to the scientists. Next, the scientists cite private or professional gatherings indoors. In addition, regular bar or restaurant visits and indoor sports increase the risk of infection.
Not a problem, according to the findings, are regular shopping and cultural or religious gatherings. Rides on buses and trains also do not increase the risk, according to the findings. Private carpools, on the other hand, should take a break during the pandemic.
Source: ntv.de/picture: pixabay.com
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