SARS-CoV-2 must somehow leap from an animal host to a human before it can tear the world, kill millions and die as we know it. It was.
The exact route taken by the virus is hotly debated, but the data suggest that the original reservoir of the SARS-CoV-2 precursor virus was probably a bat.
“It is reasonable to believe that SARS-CoV-2 is ultimately derived from bats, because so many related viruses circulate in bats.” CoronavirusDr. Ameshua Darja, an infectious disease expert and senior scholar at the Johns Hopkins Health and Safety Center in Baltimore, said. The previously epidemic-causing related coronaviruses, MERS-CoV and SARS-CoV, both evolved in bats and jumped into humans via intermediate species (camels for MERS and civet for SARS).
At the beginning of the pandemic, researchers at the Wuhan Institute of Virology said Coronavirus (RaTG13) Previously found in horseshoe-shaped bats (RaTG13)Rhinolophus affinis), According to nature.. The RaTG13 genome is 96% identical to the SARS-CoV-2 genome and is the most closely related coronavirus ever found.
However, a 4% difference in the genome means that about 50 years have passed since they last shared a common ancestor. This suggests that intermediate species may still be involved, according to Nature.
Some of those differences are in an important part of the genome. For example, the genes encoding the viral peplomer used by the virus to bind to human cells, especially the receptor binding domain, where the virus latches into human cells, differ between RaTG13 and SARS-CoV-2. , Adalja told Live Science. These significant differences “explain why SARS-CoV-2 is not RaTG13, but a virus that invaded humans and caused a pandemic,” Adalja said.
According to a study published in the journal in June 2020, the next closest bat coronavirus (RmYN02) genome is 93.3% similar to SARS-CoV-2. Current biology.. A related coronavirus was also found in the chamel horseshoe-shaped bat (Rhinolophus shameli) Sampled in Cambodia in 2010 and recently analyzed World Health Organization (WHO) Report The genomes of these coronaviruses (RshSTT200 and RshSTT182) were 92.6% similar to those of SARS-CoV-2.
“The results suggest that the geographical distribution of SARS-CoV-2 related viruses is much wider than previously expected,” the WHO report said.
Scientists do not yet know where, how, and when the changes required for SARS-CoV-2 to infect human cells have evolved. This process may have occurred in bats. Alternatively, the virus may have jumped from a bat to another species, such as the scale armor, where it evolved further.
More than a century ago, one strain of coronavirus circulating in bats produced the Pangolin coronavirus known as SARS-CoV-2, RaTG13, and Pangolin-2019, according to one study. Live science previously reported.. The ancestors of the Pangolin-2019 virus may have been different from the other two at the time. Then, in the 1960s or 1970s, the strain was again split in two, creating the RaTG13 ancestor and the SARS-CoV-2 ancestor.
Another more recent study published in the journal cell We have discovered that a single mutation may have given the coronavirus the ability to infect human cells, but it is not clear when or in which animal the virus acquired this mutation, Science news reported..
Scientists discovered it Pangolin Coronavirus has 85.5% to 92.4% genomic similarity to SARS-CoV-2. According to another study published in Nature in March 2020.. This raises the possibility that pangolin was an intermediate host for SARS-CoV-2.
According to a WHO report, “Evidence from previous studies and targeted studies has revealed the most relevant virus in bats and pangolins, which may be a reservoir of SARS-CoV-2. It has been suggested. ” However, “viruses previously identified from both bats and pangolins are sufficiently similar to SARS-CoV-2 to function as direct precursors to SARS-CoV-2.”
WHO reports suggest that mink and cats are also susceptible to SARS-CoV-2, and that such animals may also function as “potential reservoirs.”
However, according to the report, research to look for such viruses in potential reservoir species has not been systematically conducted, “potential reservoir hosts are significantly undersampled.” In other words, the potential spillover host may be sitting just below our nose and we haven’t done enough testing to find it yet.
“There may be unthinkable animals,” said Adalja, who became an intermediate host for the new coronavirus.
It is not easy to disperse the origin of SARS-CoV-2 or the virus that spreads to humans. “When the virus jumped into humans, it didn’t announce it to the world,” Adalja said. The virus is believed to be the first epidemic in China in the fall of 2019, which is also the beginning of the flu season. Early cases of COVID-19 may have been assumed to be influenza cases. That is, he said, COVID-19 was not diagnosed until the coronavirus became more widespread. “The Chinese government was not transparent about the early days of the pandemic and did not allow access to many ongoing studies,” he added.
“No one has identified a virus that is 100% identical to SARS-CoV-2 in any animal, so there is still room for researchers to ask about other possibilities,” said a vaccine infectious disease organization in Saskatchewan, Canada. Said Arinjay Banerjee, a virologist at. ,Was told Associated Press.. One of those possibilities is the “Laborique theory”. This suggests that the virus did not fly from animals around the world to humans, but accidentally spilled from samples to lab workers.
“I think it’s possible,” Adalja said. “We know that there were laboratories dealing with very similar coronaviruses, including RaTG13, and we know that there are biosafety concerns in all laboratories. This possibility needs to be thoroughly investigated, and the Chinese government needs to remain transparent, he added.
Still, with current data, he said, most experts support the hypothesis that SARS-CoV-2 has spilled from animals around the world. He said it would be important to elucidate the origin in order to prepare for the next pandemic. For example, he added, he knows which animals can help reduce human interaction if the virus bounces from intermediate animals to humans.
“This is not the last coronavirus emergency we face,” Adalja said. “Understanding and elucidating the early stages of the SARS-CoV-2 pandemic is critical to improving resilience to the next pandemic and preparing for future emerging and zoonotic diseases. . “
Originally published in Live Science.
Which animal did the new coronavirus come from?
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