E.t remains a merciless race. The virus or us. That’s how we want to see it. We should see it that way too. Keep up. But after a year of pandemic without a break, after two million Covid 19 deaths worldwide and officially more than 90 million reported infected people and above all with the prospect of a new, perhaps decisive phase in the evolutionary race between the pathogen and its host, is called it is to look the opponent and his strengths openly in the eye. It is quite possible that evolution is not on our side.
Editor in the features section, responsible for the “Nature and Science” section.
A month ago, the new danger was given a name that is easily misleading: “British variant”. It is a line of the Sars-CoV-2 pathogen, a combination of seventeen mutations in the virus genome, which was first described in England, but in no way necessarily originated there. This variant has now been identified in 43 countries, virus genomes with the corresponding profile from almost three dozen countries are stored in the “Gisaid” gene database. No question: This virus variant, scientifically as B1.1.7. known is something special. In England and Ireland, the spread of these mutants in the past three weeks has apparently led to a rocket-like, previously unprecedented increase in the number of corona cases.
Fitness benefits for the virus
Before the New Year, in week 51, their share of the viruses genetically sequenced in Ireland from Covid 19 patients was just under eight percent, two weeks later it was 25 percent. The new variant displaces the “old” virus strains. Coincidence? Probably not. From various studies – epidemiological data, experiments and modeling – the virologists conclude: This special combination of mutations gives the variant an evolutionary advantage, i.e. more fitness. It is transmitted more easily, and people can become infected more quickly.
Such fitness benefits often arise randomly and are usually difficult to determine. Since the virus spread in humans, there have certainly been various such coincidences, new mutations that bring the virus fitness benefits. D614G, for example, a single mutation that appeared in February (first in Munich and China), now dominates in all Sars-CoV-2 viruses currently circulating. They tried to understand them for months. In December, the mutation in the spike protein of the pathogen was transferred to a “Science” publication: By exchanging an amino acid in the spike protein, the virus actually binds more easily to the ACE2 receptor and can multiply more quickly. In principle, a similar situation as with variant B1.1.7. – with the crucial difference, however, that the combination of so many mutations in one variant, the respective biological effect of which is so far only marginally understood, apparently brings an even greater fitness advantage.
The number of reproductions (R value) of the pandemic pathogen is increased by 0.4 to 0.6, according to scientists working with Neil Ferguson and Erik Volz at Imperial College. British government scientists speak of a 50 percent increase in transmission rate. Translated into the Corona measures, this means: A lockdown, which was previously able to push the R value to 0.7 and thus halve the number of new infections every week, is no longer sufficient to contain the B1.1.7 variant. Instead, the R value would rise above one and the number of cases would also increase – and with it the number of Covid 19 victims. To make it even clearer: An R value of 1.0, at which each infected person infects another and thus keeps the number of cases in any region stable at a thousand new infections per month, would have to reckon with ten thousand new infections in a month with the variant .