Much has been argued about the origin of the novel coronavirus. US President Trump christened it the China virus and speculated that it came from a laboratory in Wuhan. Beijing claimed American soldiers might have brought the virus to China when they traveled to Wuhan for a military sports event.
China’s foreign minister has now again resisted that China is internationally regarded as the country of origin of the corona outbreak. Just because China was the first country to report the existence of the virus, it does not have to mean that the virus also comes from China, Wang said on a visit to Norway on Thursday, according to Reuters news agency. There have been reports that the pathogen may have occurred earlier elsewhere in the world. In fact, the virus was found in wastewater samples from last November in Brazil and in wastewater samples from last December in Italy. The first major outbreak at an animal market in Wuhan, China, occurred in late December. In China, too, there were cases in November. And an earlier find in a wastewater sample from Barcelona from last March was scientifically heavily doubted.
China is the country of origin of the corona virus
As a new study now shows, the virus is likely to come from China, as suspected. However, it was neither created on the market in Wuhan nor escaped from a laboratory. Instead, it appears to have existed for a long time in a form that is contagious to humans – but previously only attacked bats.
Bats were suspected to be the reservoir of the novel coronavirus early on, as were pangolins (pangolins), which are considered a delicacy in China and were sold on the market in Wuhan. On the other hand, scientists quickly considered it unlikely that it would develop in the laboratory because the RNA, the genetic material of the virus, shows no traces of artificial manipulation. It was unclear, however, when and how the virus acquired the ability to infect humans – and thus became a zoonosis, a disease that can be transmitted between humans and animals.
The study that was published in the journal Nature Microbiology at the end of July has now provided new insights into this. An international team of scientists had investigated in more detail how old individual sections in the virus genome are and what ancestry is therefore likely.
Hereditary information is almost identical to that of the bat virus
Sars-CoV-2 has the greatest genetic similarity with a bat virus called CoV RaTG13. Researchers had this virus First discovered in 2013 on a horseshoe bat in the Chinese province of Yunnan, 1,600 kilometers from Wuhan. The genetic information of this virus and Sars-CoV-2 is 96 percent identical, which is why scientists assume a common origin for the two viruses. However, these have developed as separate lines for 40 to 70 years.
Of all things, the gene segment that facilitates binding to human cells is more similar in Sars-CoV-2 to a coronavirus that occurs in pangolins. That is why the idea has been around for a long time that Sars-CoV-2 could have arisen through a gene exchange between bat and pangolin coronaviruses. However, the authors of the new study found no evidence of this: at the corresponding point in the genome, no gene exchange with pangolin coronavirus had taken place. Even if pangolins transmit the bat virus to humans as an intermediate host, they would not have contributed anything to their adaptation to humans, according to the researchers.
In theory, the virus has long been contagious to humans
Instead, they assume that Sars-CoV-2 already had the corresponding genes before it was split off from the other bat line – that is, 40 to 70 years ago. Presumably the closely related bat line from Yunnan once possessed the ability to infect humans, but then lost it again.
It could also be that other coronaviruses, which are infectious for humans, have been circulating in bats for a long time. However, it is currently “impossible to estimate” how many such lines there are, the scientists write. It is also difficult to discover them in people before an outbreak occurs. The new findings would therefore show once again how important a global monitoring system is for such outbreaks.