Scientists in China have found 24 previously unknown coronavirus species - four of them closely related to the one which causes COVID-19 and three similar to the virus behind the SARS epidemic of 2003.
Perhaps most worrying, all of them were found in bats living in southwestern China in an area about the size of Taupō.
The genetic diversity in such a small area in Yunnan, far from the suspected epicentre of the COVID-19 outbreak in Wuhan, surprised the scientists behind the research.
One in particular - dubbed RpYN06 - shared 94.5 percent of its genome with SARS-CoV-2, the virus that's killed nearly 3 million people since the start of last year.
"Aside from the spike gene, RpYN06 possessed a genomic backbone that is arguably the closest to SARS-CoV-2 identified to date," the study, published online last week, said. Luckily for us, it's the spike protein that largely determines how successful a virus is at infecting our cells.
The exact site the new viruses were discovered wasn't revealed, but the scientists said it was "striking" that so many were found in such a small area - about 1100 hectares, or a circle about 3.3km across.
"These results clearly demonstrate that SARS-CoV-2 related viruses continue to circulate in bat populations, and in some regions the prevalence of SARS-CoV-2 related coronaviruses might be relatively high... It is therefore essential that further surveillance efforts should cover a broader range of wild animals in this region to help track ongoing spillovers of SARS-CoV-2, SARS-CoV and other pathogenic viruses from animals to humans."
It's believed the SARS-CoV-2 virus originated in bats, perhaps passing through another animal such as the pangolin before getting the ability to infect humans.
The genetic diversity found "increases the difficulty in resolving the origins of SARS-CoV-2 and other pathogenic coronaviruses", the scientists said. The World Health Organization is expected to release the results of its investigation into the origins of the virus sometime this week.
"Bats across a broad swathe of Asia harbor coronaviruses that are closely related to SARS-CoV-2 and that the phylogenetic and genomic diversity of these viruses has likely been underestimated," the study said.
Other similar viruses have been found in recent months across much of southeastern Asia, the South China Morning Post reported, and in addition to genetic diversity, politics might get in the way of finding SARS-CoV-2's origin.
"To find the origin of a pandemic, these are the most hopeful areas," one scientist told the paper - opting to remain anonymous.
"Many scientists won't say it out loud because this may sound politically incorrect. No country in southeast Asia wants to be linked to the origin of the virus. I have some colleagues in Yunnan right now trying to work with scientists in neighbouring countries on bat viruses, but a lot of politics has got in the way."
He said "conspiracy theories and racial discrimination" were getting in the way of much of the research. The US, under former President Donald Trump, routinely hinted SARS-CoV-2 might have been developed in a Chinese lab, and released either accidentally or deliberately.
Most scientists have rejected this possibility, saying there's strong evolutionary evidence it developed naturally.
The scientific paper, 'Identification of novel bat coronaviruses sheds light on the evolutionary origins of SARS-CoV-2 and related viruses', is yet to be peer-reviewed.
SARS-CoV-2 has killed at least 2.67 million people since being discovered in late 2019. The related SARS virus, now dubbed SARS-CoV-1, was much more lethal - but killed fewer people, as most patients weren't infectious until they showed symptoms. In contrast, people can spread SARS-CoV-2 without even realising they have the virus.