"Chan and Ridley write with an urgency...that inspires gripping depictions of what viruses are, how infectious-disease laboratories work and wonderfully lucid descriptions of bats. . . . They powerfully recount how dangerous pathogens can both leak from a lab and emerge in nature." (New York Times Book Review)  Understanding how Covid-19 started is crucial for the future of humankind. Viral is the most incisive and authoritative book about the search for the source of the virus. A new virus descended on the human species in 2019 wreaking unprecedented havoc. Finding out where it came from and how it first jumped into people is an urgent priority, but early expectations that this would prove an easy question to answer have been dashed. Nearly two years into the pandemic, the crucial mystery of the origin of SARS-CoV-2 is not only unresolved but has deepened.  In this uniquely insightful book, a scientist and a writer join forces to try to get to the bottom of how a virus whose closest relations live in bats in subtropical southern China somehow managed to begin spreading among people more than 1,500 kilometres away in the city of Wuhan. They grapple with the baffling fact that the virus left none of the expected traces that such outbreaks usually create: no infected market animals or wildlife, no chains of early cases in travellers to the city, no smouldering epidemic in a rural area, no rapid adaptation of the virus to its new host--human beings.  To try to solve this pressing mystery, Viral delves deep into the events of 2019 leading up to 2021, the details of what went on in animal markets and virology laboratories, the records and data hidden from sight within archived Chinese theses and websites, and the clues that can be coaxed from the very text of the virus's own genetic code.  The result is a gripping detective story that takes the reader deeper and deeper into a metaphorical cave of mystery. One by one the authors explore promising tunnels only to show that they are blind alleys, until, miles beneath the surface, they find themselves tantalisingly close to a shaft that leads to the light.