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What are the origins of the covid-19 pandemic?

According to a study carried out by Nature, SARS-CoV-2 likely originated among bats in Southeast Asia, but there is also an intermediary animal.

A woman looks at face masks for sale at a market in Hong Kong on February 17, 2022, as the city faces its worst Covid-19 outbreak since the start of the pandemic.

A new study on the possible origins of covid-19 describes the hypothesis that coronavirus SARS-CoV-2, the root of the pandemic that has swept across the globe over the past two years, most likely originated among bats that inhabit the limestone caves of Southeast Asia and China.

The research, published in scientific journal Nature by a group of investigators from the Institut Pasteur in Paris, explains that coronaviruses that are very similar genetically to SARS-CoV-2 have been detected in populations of these bats in northern Laos. These animals would have the ability to infect humans in a similar way to the first strains of SARS-CoV-2 that caused the pandemic.

After studying 645 bats in the caves of northern Laos, up to three viruses were detected that are extensively linked to SARS-CoV-2. The genetic sequences encoding the binding regions of ACE2 - a human cell receptor used to enter human cells - in these coronaviruses are very similar to those of SARS-CoV-2. In fact, bat viruses are able to bind to these receptors more efficiently than the virus that causes covid-19.

Animal covid intermediary “probable or very probable”

According to a study conducted by the World Health Organization (WHO) a year ago, the most likely scenario for the transmission of SARS-CoV-2 from bats to humans involved one or more intermediary animals that as yet have not been identified. The research also stated that it is “extremely unlikely” that the virus originated in a laboratory, as covid-19 was not circulating in Wuhan, its point of origin, until December 2019.

The WHO investigation put forward four possible theories as to the origin of the virus: direct contagion from an animal to a human, which it termed as “possible or probable”; an intermediary animal between an infected animal and humans, which is “probable or very probable”; that the virus reached humans through food products, which is classified as “possible”; or that covid-19 was the result of a laboratory accident, which the WHO said was “extremely unlikely.”

"One of the world’s hottest regions, epidemiologically speaking"

Jordi Serra Cobo, professor of the Department of Evolutionary Biology, Ecology and Environmental Sciences of the University of Barcelona, told Spanish newspaper El Mundo that he saw plenty of merit in the Institut Pasteur research as Southeast Asia is in “one of the world’s hottest regions, epidemiologically speaking,” adding there is a “great diversity of viruses” there and that coronaviruses have been in circulation in the region “for centuries.”

However, the Cobo states that “direct transmission of a coronavirus from a bat to a human has never been observed.”

“In that sense, the fact that bats have been found to be capable of infecting human cells does not mean that there has necessarily been a species jump from bat to human,” the expert added. As interaction between bats and humans is “relatively small,” it is probable that an “intermediary species” closer to human activity could be the transmitter of covid-19.