Experts fear an as-yet unknown animal could be hiding a deadly virus that may trigger another pandemic - killing millions.
Scientists are reportedly racing against time to find 'Animal X', which could be the source of the next global disease - or 'Disease X'.
The World Health Organization has warned the threat from zoonotic disease, where infections jump from animals to humans, is an emerging danger.
Experts have said previously that it is likely Covid-19 originated in bats and pangolins, before it was transferred to people.
And bird flu, SARS, MERS, Nipah and yellow fever are all other examples of diseases which originated in animals before the viruses mutated and leapt species.
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Anthony Lockett, a medical doctor in infectious diseases, has now told The Sun Online how bats could well be the source of the next pandemic.
He said: "The species that could harbour Disease X are bats and birds as both can fly and travel long distances.
"Bats' migratory patterns can be disturbed leading to the spread of disease, as was seen in Australia a few years ago, when bats spread disease to humans."
And Dr Josef Settele, from the Helmholtz-Centre for Environmental Research, a co-author of a new UN-level study on future pandemics, added: "In principle any species could be a source.
The probability is higher for groups where there are more species like rats and bats.
"In the end, it depends on the adaptability of the species."
Environmental writer John Vidal recently revealed diseases "as contagious as measles, as deadly as Ebola" could still mutate and devastate human populations.
Many diseases - like Ebola, and Covid-19 - are thought to have infected humans through the consumption of contaminated meat.
Vidal has spoken to experts from across the world who have made gloomy predictions that the worst is possibly yet to come as he writes a book uncovering the link between nature and disease.
Writing in the Daily Mail, Vidal explained that ecologists at University College London (UCL) report that 335 new and potentially fatal diseases have emerged globally since 1945.
More than 200 are zoonoses, viruses, bacteria, parasites, fungi and prions.
The microbes, which occur naturally in wild and domesticated animals, are now being transmitted to humans, according to Vidal.
He added: "When will we really wake up to the greatest new threat of our age?
"Mankind has changed its relationship with both wild and farmed animals, destroying their habitats and crowding them together - and the process is only accelerating.
"If we fail to appreciate the seriousness of the situation, this present pandemic may be only a precursor to something far graver still."
"The nightmare scenario that governments are having to face up to is the emergence of a new disease - or a new strain of an older one - which is as contagious as, say, measles, and as deadly as Ebola.
"Then humanity could face a far worse pandemic than Covid-19, possibly on the scale of the Black Death, which killed up to one in three people in Europe in the Middle Ages."
