Scientists have discovered the closest known relatives of Covid in more than 12% of persons living in rural Myanmar for the first time, indicating that “zoonotic spillover” is occurring.
Between 2017 and 2020, an international team of experts from the United States, Singapore, and Myanmar examined the blood of 693 persons in Myanmar. The participants came from villages in rural Myanmar that were involved in extractive industries and bat guano gathering.
The findings, published in the International Journal of Infectious Diseases, revealed that 12.1% of patients tested positive for sarbecoviruses, the Coronavirus family to which SARS-CoV belongs.
These viruses, which have the ability to spread from animals to humans, had never been found in humans before. Thus yet, they have only been found in bats.
“Exposure to diverse sarbecoviruses among high-risk human communities provides epidemiologic and immunologic evidence that zoonotic spillover is occurring,” wrote Tierra Smiley Evans, from University of California, and authors in the paper.
While the study found exposure to a variety of bat and pangolin sarbecoviruses, the data suggests that RaTG13 is the sarbecovirus that spreads the most commonly to people in Myanmar.
RaTG13, the closest known related of SARS-CoV-2, was identified in a cave in Yunnan, China, near the border with Myanmar, by Pasteur Institute researchers in 2020. Overall, it was 96.1 percent identical to SARS-CoV-2, and the two viruses likely shared a common ancestor 40-70 years ago, comparable to the newly discovered viruses.
RaTG13 was found in 32% of the 70 samples collected from workers working in elephant logging camps. BANAL-52 was also discovered in about 1.4% of the participants.
Pasteur Institute researchers identified BANAL-52, which shares 96.8 percent of its genome with SARS-CoV-2, in horseshoe bats in Laos in 2021.
“Our findings underpin the critical importance of continued surveillance at the rural wildlife-human interface in Southeast Asia, where some of the highest levels of known mammalian diversity exist and where future emergence of zoonotic diseases is likely,” the researchers said.