Coronaviruses discovered in Laotian bats are surprisingly adept at infecting human cells, showing that such deadly features can indeed evolve outside of a lab.

Samples of viruses from bats living in the wild in Laos, Cambodia, China and Thailand have given researchers new clues to the origin of the virus that causes Covid-19, suggesting that wild strains could have easily mutated into the deadly virus that has caused a global pandemic. Some of the wild strains very closely resemble SARS-CoV-2, and carry a microscopic hook that lets them cling on to human cells.

The newly discovered viruses were first encountered in the summer of 2020, half a year into the coronavirus pandemic, when scientists traveled into the forests of northern Laos to catch bats that might harbor close cousins of the pathogen. In the dead of night, they used mist nets and canvas traps to snag the animals as they emerged from nearby caves, gathered samples of saliva, urine and feces, then released them back into the darkness, the New York Times reports.

The fecal samples turned out to contain coronaviruses, which the scientists studied in high security biosafety labs, known as BSL-3, using specialized protective gear and air filters. Three of the Laos coronaviruses were unusual: They carried a molecular hook on their surface that was very similar to the hook on the virus that causes Covid-19, called SARS-CoV-2. Like SARS-CoV-2, their hook allowed them to latch onto human cells.

“That really puts to bed any notion that this virus had to have been concocted, or somehow manipulated in a lab, to be so good at infecting humans,” said Michael Worobey, a University of Arizona virologist who was not involved in the work.

These bat viruses, along with more than a dozen others discovered in recent months in Laos, Cambodia, China and Thailand, may also help researchers better anticipate future pandemics. The viruses’ family trees offer hints about where potentially dangerous strains are lurking, and which animals scientists should look at to find them.

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