It is now known that gene variant B.1.1.7, originally discovered in Great Britain at the end of the year, is significantly more contagious than other variants of the coronavirus. How much more precisely it is contagious is not yet known with certainty. British researchers first estimated that B.1.1.7 is 50 to 70 percent more contagious. PHE, the UK health authority, now estimates 25 to 40 percent, and other scientists 43 to 82 percent.
What we do know, however, is that the gene variant is currently spreading just as rapidly in Germany as it was before in Great Britain. Within just two weeks, their share in this country has increased from just under 6 to over 22 percent. Health Minister Jens Spahn (CDU) therefore expects “that the variant could soon become the dominant one for us too”.
But why B.1.1.7 is so much more contagious, there have only been speculations so far. Some experts had assumed that the gene variant brings with it a higher viral load in the infected – but whether this is true was not yet known. Researchers led by Stephen Kissler from Harvard University have just looked at this thesis.
In a small study that has not yet been peer-reviewed, the researchers examined 65 players from the National Basketball Association (NBA). They were all infected with SARS-CoV2, seven of them were infected with B.1.1.7.
B.1.1.7 is more contagious because an infected person has a relatively high viral load for much longer
Every day the players had to do a PCR test. From the results, the researchers were able to infer how high the viral load was on each individual day and for how many days the viral load peaked – which is an indicator of how long the person affected is likely to be contagious. The result showed that the peak values in the viral load for both gene variants were comparably high, but these values persisted longer in those infected with B.1.1.7.
In other words: B.1.1.7 is not more contagious because people infected with it have a higher viral load – but because it is clearly longer have a relatively high viral load. So the cause is not the amount of viruses, but the number of days on which an affected person is contagious.
The authors of the study write: “These data provide indications that the SARS-CoV-2 variant B.1.1.7 can cause longer infections with similar viral peak concentrations compared to non-B.1.1.7 SARS-CoV-2. This extended duration can contribute to the increased transferability of B.1.1.7 SARS-CoV-2 “.
Since the study is very small and only took into account seven Covid 19 patients with the gene variant B.1.1.7, this could only be a first indication of the possible cause of the higher infection rate, according to the scientists. However, if the suspicion is confirmed, this could have an impact on the time of isolation of those infected with B.1.1.7. “If the results are confirmed by further data, a longer isolation time than the currently recommended 10 days after the onset of symptoms could be required in order to effectively interrupt secondary infections caused by this variant,” the researchers conclude.