Graubünden has the first corona mass test behind it

Graubünden has passed the first mass test – that’s what the numbers mean

Around 15,000 tests and 150 infected people discovered – this is the conclusion of the first mass Swiss crown test. The man from the Diagnostic Science Task Force explains the meaning of the results.

The canton of Graubünden has passed the first large-scale mass corona test. This Swiss-wide premiere took place last weekend: general 15,151 people a tube was voluntarily inserted into their nostrils to find out soon after if Sars-CoV-2-Viren could be measured.

This test was carried out in the three Graubünden regions Bernina, Engiadina Bassa / Val Müstair and Maloja. The first conclusion: 150 people were discovered who had been infected and did not know anything about it due to the lack of clear symptoms. This corresponds to roughly a one percent positivity rate, so the differences between the regions are not insignificant.

150 symptom-free people were isolated after the test

The canton of Graubünden published the results of the massive test on Monday afternoon. Those responsible see a clear benefit from the massive test, because asymptomatic people “contribute significantly to the spread and perpetuation of the pandemic” would be – and has just been discovered.

But what do the numbers tell us? Do we have to worry, or can health officials do business as usual based on Graubünden’s findings? We discussed it with.

The results say nothing about the number of unreported cases

Didier’s Throne, Head of the Department of “Diagnostics” of the Federal Corona Task Force, has analyzed the first results and states: “The positivity rate is rather in the low range, but that is not surprising either.” It would be more or less the same as in the massive crown tests in South Tyrol or Slovakia.

However, you do not want to compare the figures for the whole of Switzerland. ‘The Graubünden results cannot simply be extrapolated. On the one hand, only three Graubünden regions were tested here, on the other hand, the incidence value of the canton is not comparable to other parts of the country, ”says Trono. It refers to the number of people who tested positive for every 100,000 inhabitants. With this value, Graubünden is roughly in the middle of all cantons.

However, he cautions that the numbers be put on the golden scale. The reason lies in the rapid antigen test. “This test requires a higher viral load for the result to be positive.” In other words, there are an unreported number of people who are carriers of the virus but have no symptoms and tested negative. The canton of Graubünden estimates that half of those infected have not yet been “discovered”.

Massive testing alone cannot stop an epidemic

Furthermore, the results are a snapshot: “We do not know if a person who tested negative on Saturday will become ill on Monday due to a higher viral load. He would have to test the population several times. “That would be done in an ideal world, but the logistical challenges are enormous.”

But even then, such nationwide rapid tests would not stop the epidemic entirely. Throne refers to Slovakia’s experiences: Two-thirds of the country’s 5.5 million people were screened there with a huge logistical effort, where only 40-50 percent of all infected people were reportedly discovered .

However, Trono sees an advantage to Bündner’s massive test: “Now infected people know they have to isolate themselves. There are fewer people in little German-speaking Switzerland who can infect other people while traveling or in their spare time. ”

The diagnostician, however, lowers any hope in the mountainous canton: due to the “great appeal of the Engadine and the neighboring valleys”, it is to be expected that many new sources of infection will emerge in the coming days due to the expected influx of visitors, “unless strict protection measures are taken”, so Throne.