Researchers discover the origin of the coronavirus

RND Researchers discover the origin of the coronavirus A researcher takes a swab from the mouth of a bat. There are increasing signs that the virus was transmitted from bats to humans. China, Brazil, Italy, Spain: There has long been speculation about where Sars-CoV-2 originated. A study has now shown that the virus most likely spread from China to the world, as is often suspected. There is also increasing evidence that bats acted as vectors. There has been much debate about the origin of the new coronavirus. US President Trump dubbed it the China virus and speculated that it came from a laboratory in Wuhan. Beijing had claimed that American soldiers could have brought the virus to China when they traveled to Wuhan for a military sporting event. Chronology of the coronavirus The devastating coronavirus probably started at an animal market in Wuhan, China. In just a few weeks, the virus also reached Europe. China's foreign minister has now again objected to China being 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 does not mean that it also originated in China, Wang said on Thursday during a visit to Norway, according to the Reuters news agency. There had been reports that the pathogen may have appeared elsewhere in the world earlier. In fact, the virus was found in wastewater samples from Brazil last November and in wastewater samples from Italy last December. The first major outbreak at an animal market in Wuhan, China, occurred at the end of December. But there had also been cases in China in November. And an earlier discovery in a wastewater sample from Barcelona last March was scientifically strongly doubted. Did the coronavirus come from a Chinese laboratory? US Secretary of State Mike Pompeo sees "overwhelming evidence" for this - but is withholding it from the public. Corona: Mistrust of China is growing As a study has now shown, the virus may have come from China, as suspected. However, it neither originated in the market in Wuhan nor escaped from a laboratory. Instead, it has apparently existed for a long time in a form that is contagious to humans - but previously only infected bats. Bats were suspected early on as a reservoir of the new coronavirus, as were pangolins, which are considered a delicacy in China and were sold in the market in Wuhan. Scientists, on the other hand, quickly considered it unlikely that it originated in the laboratory because the RNA, the virus's genetic material, shows no trace of artificial manipulation. However, it was unclear 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 published in the "Journal Nature Microbiology" at the end of July has now provided new insights into this. An international team of scientists had examined in more detail how old individual sections of the virus genome are and which origin is therefore likely. Sars-CoV-2 has the greatest genetic similarity with a bat virus called CoV RaTG13. Researchers first discovered this virus in 2013 in 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 that the two viruses have a common origin. However, they have evolved as separate lines for 40 to 70 years. However, the gene section in Sars-CoV-2 that facilitates binding to human cells is more similar to a coronavirus found in pangolins. This is why the idea has long been 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: no gene exchange with pangolin coronaviruses had taken place at the corresponding point in the genome. Even if pangolins may transmit the bat viruses to humans as intermediate hosts, they have not contributed to their adaptation to humans, say the researchers. Instead, they assume that Sars-CoV-2 already had the corresponding genes before it split off from the other bat lineage - i.e. 40 to 70 years ago. The closely related bat lineage from Yunnan probably also once had the ability to infect humans, but then lost it again. It is also possible that other coronaviruses that are infectious to humans have been circulating in bats for some time.