Since the deadly viral disease known as severe acute respiratory syndrome (SARS) swept through the world in 2003, killing 774 people and infecting over 8,000, scientists have struggled to figure out exactly where it came from. They traced it to bats in southern China, but believed that the virus had to undergo genetic changes through an intermediary animal — the civet. But new research into the matter has found “the clearest evidence yet” that the SARS coronavirus (SARS-CoV) originated in Chinese horseshoe bats and has found similar strains that could be transferred through contact with humans.

Previous studies on bats had shown that the SARS virus they carried was close to the one that infected humans. But a major difference, in the so-called spike protein, which latches onto, and infects human cells was coded in a way that disabled infection, according to Wired. For this reason, authorities believed the virus transferred to civets in Chinese markets, where it underwent the genetic changes that allowed it to infect humans. For this reason, China began monitoring markets where bats, civets, and other wild animals were sold as food.

The study, conducted by the National Institutes of Health’s Ecology and Evolution of Infectious Diseases Initiative (EEID), has now found that genetic samples sourced from Chinese horseshoe bats over the course of a year yielded at least seven strains of SARS-like coronaviruses (SL-CoVs), two of which were more closely related to the SARS-CoV that infected humans than any other CoV previously found in bats. Going further, the researchers were able to isolate a live SL-CoV from one of the samples, which subsequently attached itself to a human cell in a culture.

“This paper indicates that the bat is the origin and that the virus can be directly transmitted to humans,” Charles Calisher, a virologist at Colorado State University, who wasn’t involved in the study, told The Wall Street Journal, adding that it “practically rules out the possibility” that civets were necessary to intermediate viral transmission.

Study author Peter Daszak says the study’s results should be a warning to people in the Chinese population, and elsewhere, that eating bats can lead to the virus’ transmission. But Christian Drosten, a coronavirus expert at the University of Bonn, Germany, stopped short of making such a conclusion, saying that the lab experiments don’t necessarily mean the virus will certainly transmit to humans. “Reception studies and cell culture aren’t everything,” he told Wired. “You would have to take the virus and see in an animal experiment whether it can, for instance, infect a primate.”

Drosten said that the study’s findings are reminiscent of the coronavirus causing Middle East respiratory syndrome (MERS), which has already killed 62 people, according to the Centers for Disease Control and Prevention. By studying the virus in these animals, researchers may be able to find the pathogens that would be responsible for future outbreaks, he said.

Source: Daszak P, Ge X, Shi Z, et al. Isolation and characterization of a bat SARS-like coronavirus that uses the ACE2 receptor. Nature. 2013.

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