In a breakthrough that provides clues for those investigating the origin of the pandemic, scientists said high levels of neutralising antibodies against coronaviruses were present in the animals in Thailand.
A team from Singapore’s Duke-NUS Medical School found SARS-CoV-2 – the virus that causes Covid-19 – neutralising antibodies in Rhinolophus bats in a Thai cave and in a pangolin at a wildlife checkpoint in the south of the country.
The findings, published in the journal Nature Communications, indicate more coronaviruses are likely to be discovered across Southeast Asia, which has a large and diverse bat population, the researchers said. Such viruses have now been found across a wide expanse measuring 4,800 km, from Japan and China to Thailand.
“Studies like this are crucial in furthering our understanding of the many SARS-CoV-2-related viruses that exist in the wild,” said Professor Patrick Casey, senior vice dean for research at Duke-NUS.
“This work is also timely as investigations into the origins of SARS-CoV-2 are ongoing and may provide further leads on the origin of this outbreak.
"Such studies also play a key role in helping us be better prepared against future pandemics as they provide a more detailed map of zoonotic threats.”
The findings were revealed as a World Health Organisation (WHO) team prepared to leave China after investigating the origins of the coronavirus pandemic – though with major questions still unanswered.
The Singapore team said their work was the first and only study to provide evidence at a molecular and antibody level that coronaviruses linked to Covid-19 are circulating in bats and pangolins in Southeast Asia.
Co-author of the study Chee Wah Tan, a senior research fellow with Duke-NUS' Emerging Infectious Diseases programme, said “cross-border surveillance” was now needed to establish how Covid-19 had spread.
Dr Supaporn Wacharapluesadee, from the Thai Red Cross Emerging Infectious Diseases Health Science Centre at Bangkok’s Chulalongkorn University, added: “This is an important discovery in the search for the origin of SARS-CoV-2, which was made possible by rapid application of cutting-edge technology through transparent international collaboration.”
On Wednesday, the WHO team departed China following a four-week trip to the city of Wuhan, where the first Covid-19 cases were detected in December 2019.
The team's major conclusions seemed to confirm what most researchers had already supposed about the virus – that bats are the most likely carriers, and that they passed it on to another animal, which passed it on to humans.
However the visit was never expected to definitively pinpoint the origin of the pandemic – an undertaking that could take years.
The Huanan Seafood Market, which had a cluster of cases at the start of the outbreak, has long been suggested as a possible place humans first became infected.
A member of the WHO panel said some of the animals sold at the market had been traced to regions that are home to bats that carry the virus that is the closest known relative of the one that causes Covid-19.
But a Chinese official said it appeared there were cases elsewhere in Wuhan around the same time as the market cluster, so it remains possible the transfer of the virus from animals to humans happened elsewhere.
The WHO team also said the suggestion the virus may have leaked from the Wuhan Institute of Virology, a lab with an extensive collection of virus samples, was unlikely as there was no evidence the virus existed in that lab or any lab anywhere in the world when the pandemic began.
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