By Martin Cole-
Scientists are claiming to have discovered more clues about how the new coronavirus could have spread from bats through pangolins and into humans as the number of infections worldwide nears six million.
Researchers writing in the journal Covid-19 Science Advances say that an examination of the closest relative of the virus found that it was circulating in bats but lacked the protein needed to bind to human cells.
The U.S-based scientists said this ability could have been acquired from a virus found in pangolins – a scaly mammal that is one of the most illegally trafficked animals on the planet.
The severe respiratory disease COVID-19 was first noticed in late December 2019 (1). It rapidly became epidemic in China, devastating public health and economy.
At the beginning of May, COVID-19 had spread to ~150 countries and infected over 3.3 million people (2). On March 11, 2020, the World Health Organization (WHO) officially declared it a pandemic.
The etiological agent(cause) of COVID-19 – severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2) was identified as a new member of the genus Betacoronavirus, which includes a diverse reservoir of coronaviruses (CoVs) isolated from bats .
Benefits
Understanding the origin of SARS-CoV-2 may help develop strategies to deter future cross-species transmissions, and also help establish appropriate animal models.
Dr Elena Giorgi, one of the study’s lead authors, of Los Alamos national laboratory, said the pangolin link had already been examined but scientists were still divided about their role in the evolution of Sars-Cov-2, the virus that causes Covid-19.
“In our study, we demonstrated that indeed Sars-Cov-2 has a rich evolutionary history that included a reshuffling of genetic material between bat and pangolin coronavirus before it acquired its ability to jump to humans,” she said, adding that “close proximity of animals of different species in a wet market setting may increase the potential for cross-species spillover infections”.
The study still doesn’t confirm the pangolin as the animal that passed the virus to humans, but it adds weight to previous studies that have suggested it may have been involved.
However, Prof Edward Holmes, an evolutionary biologist at the University of Sydney in Australia, said more work on the subject was needed. “There is a clear evolutionary gap between Sars-Cov-2 and its closest relatives found to date in bat and pangolins,” he said. “The only way this gap will be filled is through more wildlife sampling.”
The news comes as deaths in the U.S rose to more than 102,000 with 1,747,000 infections, by far the biggest total in the world.
There have been competing views about the origin of the virus, with some insisting it was man made orchestrated in a Chinese lab near the Wuhan Market, and others stating that it occurred by chance though animals.
Journalists have generally formulated their own views in accordance with the most reliable information coming in, adjusting it as new information comes on stream.
The origin of the virus is important because it helps us understand the nature of the virus and predict its behaviour according to its characteristics.
The division amongst scientist about the role of the pangolin link means certainty about the virus’s origin remains elusive, but careful studies and evaluations continues.