Well, it seems a long time ago there was no news aboutcoronavirus, so we fix the situation. With the origin of the virus still a mystery, experts from the World Health Organization (WHO) are actively planning the next steps. Meanwhile, a joint international and Chinese mission to study the origins of COVID-19, organized by WHO, released a report saying that more research is needed on almost every topic raised in the course of the work. The results presented in the report include an extensive review of the existing scientific literature and support a generally accepted understanding of the origin of the virus. It lies in the fact that the bat coronavirus, most likely, jumped to another animal and only then to a person. A similar situation was previously observed in the case of the "sibling" COVID-19, the MERS coronavirus - camels turned out to be an intermediate link in the journey and evolution of the virus.
- 1 How did COVID-19 come about?
- 2 Main theories of the origin of COVID-19
- 2.1 The intermediate host theory
- 2.2 Zoonotic overflow theory
- 2.3 Cold chain theory
How did COVID-19 come about?
Despite the fact that from the moment"Mysterious pneumonia" has spread around the world more than a year has passed, scientists still cannot say with certainty where the virus that causes COVID-19 came from. Meanwhile, the story of its origin could allow researchers to understand how to stop future outbreaks of dangerous infections. To dot the i's, in mid-January 2021, WHO sent a group of 17 international experts to Wuhan (the epicenter of the outbreak) to jointly investigate the origins of SARS-CoV-2 with Chinese scientists.
In general, the scientific community has beentalks about the zoonotic origin of COVID-19, and we also wrote about this on Hi-News.ru more than once. The zoonotic origin of the virus means that it likely jumped from animals to humans when they came into contact with an infected animal. According to the authors of the report, this contact may include handling an infected animal, eating it, or preparing the animal for sale.
However, experts do not know exactly how the virus jumped to humans, and for the final conclusion about the origin of SARS-CoV-2 it can take years... Best Comparison - SARS Outbreak2003, which was caused by a close relative of COVID-19, and ultimately traced back to one single population of bats. But looking for the culprit it took more than five years. In comparison, the source of the Ebola virus outbreaks has not yet been identified, despite decades of research.
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Main theories of the origin of COVID-19
The report explored four main theories about how the virus spread to humans; they are ranked in order of likelihood, from very likely to very unlikely.
The intermediate host theory
This theory suggests that the virus was transmitted fromthe original host animal to an intermediate host such as minks, pangolins and other pangolins, rabbits, raccoon dogs, domesticated cats, ferrets, etc., and then directly infected the person by contact of the latter with a second animal. This theory is considered the most likely.
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Zoonotic overflow theory
According to this theory, the transmission of the virus took placedirectly from the natural host of the virus - bats. The authors of the report note that the transmission of infection could occur as a result of farming, hunting or other close contacts between people or animals.
Cold chain theory
Cold chain theory suggests that transmissionSARS-CoV-2 from animals to humans may have originated through contaminated frozen foods. Frozen food contaminated with animal waste containing SARS-CoV-2 could transmit the virus to humans without any direct human-animal contact.
As part of the investigation, scientists returned to the marketHuanan seafood, associated with the first known chain of infection in Wuhan. They also visited Hubei Provincial Hospital - Integrated Chinese and Western Medicine, where some of the first cases of COVID-19 were treated - and examined the viral sequencing data. It showed that various minor variants of SARS-CoV-2 were distributed in Wuhan in December 2020. Viral sequencing also revealed that the Huanan market was most likely not the main source of the outbreak.
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Interestingly, the last, fourth theory about the leak of the virus from the laboratory in Wuhan, the researchers consider the least likely. Why I talked about in this article.
The most likely way, as found inresearch, is the first theory that the virus was transmitted from a bat to an intermediate animal, and then to humans. Based on the findings, the next steps to investigate may include tracking the first cases of the virus; examining market suppliers for unusual spikes in antibodies; and examining areas of concentration of animals that we know are susceptible to SARS-CoV-2.