Corona wave is building up: new variants can promote spread

The corona figures have risen sharply in the past week. If there were 16,826 in the previous week, there are now 25,134 lab-confirmed cases, which is about 50 percent more. If you take into account the general test fatigue and the high positivity rate of 30 percent, a high number of unreported infections by a factor of 10 can be assumed.

The trend towards an increase is also reflected in the viral load of the wastewater. Monitoring by the water research institute Eawag has shown significantly more Sars-CoV-2 in the waste water of the sewage treatment plants Werdholzli ZH, Altenrhein SG and Chur in recent days.

The number of hospital admissions also rose by 36 percent to 290 hospital admissions. The last time there were that many was early August. For example, the occupancy rate of hospitals remains stable at a low level. Currently, Covid patients make up 3.9 percent in intensive care units and 4.1 percent of all hospitalized patients.

At the beginning of autumn, however, the question arises whether a new variant could possibly cause a stronger corona wave. Three weeks ago, experts were concerned about the Omicron variant BJ.1, which appeared mainly in India, but also spread to Europe and the US. Albeit in small numbers.

BJ.1 is one of several ommicron sublines that have been extensively mutated. 14 mutations were found in the spike protein, which are more common in sites important for antibody formation. Virus specialists therefore spoke of a “malicious combination” of mutations at critical points. “But BJ.1 doesn’t seem to be spreading further,” said virus analyst Richard Neher of the University of Basel.

BQ.1.1 is a further development of BA.5, which is still the absolute dominant variant in Switzerland and worldwide. But that will change because viruses are always mutating. This is their survival strategy.

BQ.1.1. is mainly observed in Great Britain. BJ.1 already indicates a partial immune escape of the virus. This means that such a subtype is better able to evade the antibody-promoted immune system. Neher says there are now a number of other variants with mutations that indicate partial immune system escape.

These variants are mutated at three to five positions. Certain positions on the spike protein are involved. “Variants with such mutations are less well recognized by antibodies and therefore appear to have a transmission advantage,” says Neher from the Biozentrum at the University of Basel.

According to the virus sequencer, the increasing laboratory-confirmed cases show that the new corona wave seems to have already started. “This can be accelerated by these new variants,” says Neher.

But even if these different variants such as BQ.1.1, BJ.1 in Austria or BA.2.75 and its sub variant BA.2.75.2 have a transmission advantage, this does not mean that these sub variants are also more aggressive. BJ.1 and BA.2.75 have also been found in Switzerland, albeit in very small numbers.

Like every fall, there are several reasons for the acceleration of the wave. The cold weather plays an important role in both cases.