The former director of the Institute for Immunology at the University of Bern explains why everything you think you know about the virus is probably wrong:
This is not an accusation, but a ruthless taking stock [of the current situation]. I could slap myself, because I looked at Sars-CoV2- way too long with panic. I am also somewhat annoyed with many of my immunology colleagues who so far have left the discussion about Covid-19 to virologist and epidemiologist. I feel it is time to criticise some of the main and completely wrong public statements about this virus.
Firstly, it was wrong to claim that this virus was novel. Secondly, It was even more wrong to claim that the population would not already have some immunity against this virus. Thirdly, it was the crowning of stupidity to claim that someone could have Covid-19 without any symptoms at all or even to pass the disease along without showing any symptoms whatsoever. […]
The penny dropped only when I realised that the first commercially available antibody test [for Sars-CoV-2] was put together from an old antibody test that was meant to detect Sars-1. This kind of test evaluates if there are antibodies in someone’s blood and if they came about through an early fight against the virus. [Scientists] even extracted antibodies from a llama that would detect Sars-1, Sars-CoV-2, and even the Mers virus. It also became known that Sars-CoV-2 had a less significant impact in areas in China where Sars-1 had previously raged. This is clear evidence urgently suggesting that our immune system considers Sars-1 and Sars-Cov-2 at least partially identical and that one virus could probably protect us from the other. […]
In mid-April, work was published by the group of Andreas Thiel at the Charité Berlin. A paper with 30 authors, amongst them the virologist Christian Drosten. It showed that in 34 % of people in Berlin who had never been in contact with the Sars-CoV-2 virus showed nonetheless T-cell immunity against it (T-cell immunity is a different kind of immune reaction, see below). This means that our T-cells, i.e. white blood cells, detect common structures appearing on Sars-CoV-2 and regular cold viruses and therefore combat both of them. […]
So if we do a PCR corona test on an immune person, it is not a virus that is detected, but a small shattered part of the viral genome. The test comes back positive for as long as there are tiny shattered parts of the virus left. Correct: Even if the infectious viruses are long dead, a corona test can come back positive, because the PCR method multiplies even a tiny fraction of the viral genetic material enough [to be detected]. That’s exactly what happened, when there was the global news, even shared by the WHO, that 200 Koreans who already went through Covid-19 were infected a second time and that there was therefore probably no immunity against this virus. The explanation of what really happened and an apology came only later, when it was clear that the immune Koreans were perfectly healthy and only had a short battle with the virus. The crux was that the virus debris registered with the overly sensitive test and therefore came back as “positive”. It is likely that a large number of the daily reported infection numbers are purely due to viral debris.
This may explain why the behavior of the virus appears to be largely unaffected by government action; cross-country comparisons suggest no obvious patterns. Japan, for example, did little to combat the virus and has suffered less than 1,000 deaths, to the media’s great puzzlement.