Researchers call for sampling in wider geographical regions to pin down source
A systematic survey of China's bat population that covered all key regions and consolidated data spanning more than a decade has found no traces of SARS-CoV-2 or closely related viruses in any samples, suggesting that the virus causing the COVID-19 pandemic might not circulate widely among the country's bats, according to a new study.
The findings support conducting extensive investigations in Southeast and South Asia, and in particular in regions where bat species susceptible to the virus live but not enough sampling has been performed, the study, released by Chinese researchers on Monday, said.
The paper was released on In Review, a preprint service provider jointly developed by the online platform Research Square and the international journal Nature. It was conducted by researchers from several institutes, including the Chinese Academy of Medical Sciences& Peking Union Medical College and Shenyang Agricultural University.
Scientists around the world have pinpointed bats as one of the most likely animal reservoirs of the virus. However, no bat specimen has been found to carry viruses that are genetically close enough to SARS-CoV-2, the novel coronavirus linked to COVID-19, to count as its immediate ancestor, and international experts are calling for intensified research in that field.
Wu Zhiqiang, a researcher from the Chinese Academy of Medical Sciences & Peking Union Medical College's Institute of Pathogen Biology, said the new study provided a macroscopic view of coronaviruses harbored by bats in China.
Wu is also the corresponding author of the study.
The new study tested 102 samples taken from meat stalls at the Huanan seafood market in Wuhan, Hubei province, as well as throat and anal swabs from more than 13,000 bats collected at over 700 locations across China.
Sampled locations included nearly all known hot spots for sarbecovirus－a subgroup of coronavirus that includes SARS-CoV-2－in South China in the past five years, according to the study.
Despite the great depth and size of sampling, researchers said no traces of viruses highly homologous to SARS-CoV-2 were detected, "indicating that coronaviruses related to SARS-CoV-2 might not actively circulate among bats in China".
"The study has revealed that the likelihood of bats in China carrying SARS-CoV-2 is very low, and the virus' immediate ancestor is more likely to be in wild animals living in places south or southwest of China," Wu told China Daily.
Wu said more international collaboration aimed at surveying bats outside China, especially on the Indochinese Peninsula, is needed to hunt down the natural reservoir of the virus.
The call for conducting bat sampling and testing in wider geographical regions was also raised in a review published last week by Chinese researchers on Lancet, a prestigious international journal.
The review said a variety of evidence had emerged recently and warranted further global investigation of the origin of the virus that was not confined to China.
Key evidence included that horseshoe bats found in Cambodia, Thailand, Japan and southwestern border areas of China, as well as Malayan pangolins captured in anti-smuggling campaigns, all carry coronaviruses similar to SARS-CoV-2.
"The next phase of investigation of SARS-CoV-2's origin should not entirely focus on China; instead a worldwide search at different geographical locations should be carried out to identify where and when the first animal-to-human transmission occurred," it said.
