Animal X' hiding a deadly virus that could trigger a pandemic worse than the Black Death.It is feared it could kill as more than 75 million people worldwide with unknown viruses hiding unseen in animals around the world before mutating and crossing over to humans.Experts believe Covid-19 jumped from animals to humans, probably from bats, and now scientists are in a race against time to find the potential source of the next one.World Health Organization (WHO) officials have warned the threat from a zoonotic disease, the term for where infections jump from animals to humans.WHO estimate around one billion cases of illness and millions of deaths occur each year from such diseases.Dr Josef Settele, from the Helmholtz-Centre for Environmental.