Nothing in recent history can compare to the extent and impact of the SARS-CoV-2 coronavirus pandemic, which causes COVID-19. The epidemic seems to have always been ahead of the slow or hesitant response of many countries, except for Singapore, South Korea or Japan, and its behavior has surprised epidemiologists around the world. But it is also true that China has shown that drastic and rapid measures can contain the epidemic, after months of effort, and that Science has never been more prepared than now to fight this virus.
Genetics has been crucial. Thanks to it, the genetic material of this virus has been sequenced very quickly, and the first vaccine based on this knowledge has been tested in record time, just 63 days after obtaining this sequence. An article published today in “Cell”, and produced by two of the scientists who have had a more prominent role in investigating the SARS-CoV-2 genome, has reviewed everything that is known and what is not known about this enemy. . Researchers have written about the origin of the virus, its relationship with bats and pangolins and about the reasons that have surprised the world.
“The emergence and rapid dispersal of COVID-19 represents the perfect epidemiological storm”
“The emergence and rapid spread of COVID-19 represents the perfect epidemiological storm,” write the article’s authors, Yong-Zhen Zhang and Edward C. Holmes, researchers at the Centers for Disease Control and Prevention in China and the University of Sidney (Australia), respectively. “A respiratory pathogen with a relatively high level of virulence, originating from a family of viruses that has the unusual ability to jump over species barriers, which emerged in a large population center and communications hub just before the time of more trips of the year: the Chinese Spring Festival ».
Very contagious and elusive
This virus was triggered in the right place and at the right time, and it is also not just anyone. In the years 2003 and 2012, two viruses of the coronavirus family (SARS-CoV and MERS-CoV) already jumped from animals (civets and camels, respectively) to humans, but these were not as successful in transmitting between people. . “It is clear that SARS-CoV-2 is more infectious than SARS-CoV and MERS-CoV and that individuals can transmit viruses when they are asymptomatic or presymptomatic, although how often they do is unknown,” they have written.
All this would explain why SARS and MERS produced limited epidemics but this has triggered a pandemic of unforeseeable consequences: “The considerable local transmission of SARS-CoV-2 caught by surprise,” write Zhang and Holmes. Therefore, they emphasize that it is crucial to study the characteristics that make this virus so transmissible.
Analysis of the genome suggests that one of the causes of it being so contagious could be in the presence of a change in the structure of the S protein, which allows the virus to contact the cells it is going to infect. Specifically, the structure of the SARS-CoV-2 protein S has a site or domain capable of binding to furin, a protein from animal cells, which “probably increases the infectivity of the virus,” they explain.
The mysterious origin of the virus
Another key that has made SARS-CoV-2 surprise humanity is that we do not know its origin and what was the route by which it began to spread between people. Homes and Zhang highlight the evidence pointing to the Wuhan seafood market as a possible source of the coronavirus outbreak, when this pathogen “jumped” from animals to humans. But the reality is more complex.
The genome sequences obtained on surfaces of this place “suggest that the market played an important role in the appearance of the virus, but it is not clear if these samples are from people who inadvertently deposited this material or if they come from animals present there.” Given the lack of animal samples at this time, the authors believe that “it will be difficult, if not impossible, to accurately identify an animal (virus) reservoir in that location.”
A study published this week in “Nature Medicine” ruled out that the coronavirus had been created in a laboratory, after analyzing its genome. “There is simply no evidence that SARS-CoV-2 came from a laboratory,” said Holmes. “This is actually the kind of natural disease onset that researchers in the field, like me, have been warning about for many years.”
In search of the intermediate host
The similarity of the SARS-CoV-2 sequence to other bat coronaviruses indicates that it comes from these animals, but exactly what their role has been is unknown. Furthermore, the changes in its genome indicate that the virus may have entered an intermediate host. Just today, a group of researchers, including Edward C. Holmes, have published an article in which they have identified a coronavirus very similar to SARS-CoV-2 in the pangolin population of southern China.
The article concludes that SARS-CoV-2 will likely become the fifth coronavirus to infect humans. “Coronaviruses clearly have the ability to bypass species barriers and adapt to new hosts, so it stands to reason that more will emerge in the future.”
Therefore, understanding the route followed by the coronavirus and its genome is not only helpful to fight the current pandemic, but also to prepare for future threats from other coronaviruses in other animal species. Therefore, they recommend tightening legislation against illegal animal trafficking, banning the sale of mammals and birds in these fresh Chinese markets, and further investigating the diversity of coronaviruses that infect mammals. .