Things are moving so fast. Our lives are not what they seemed to be just a month ago, even a week ago. So much of what we have been reading, watching, hearing, seems no longer relevant to us. How can publishing possibly keep up? Paolo Giordano is a 38-year-old Italian writer who holds a PhD in theoretical physics. His novel The Solitude of Prime Numbers, a carefully structured narrative about pivotal moments in the lives of two characters, won Italy’s top literary prize, the Premio Strega, in 2008 and sold more than a million copies. On February 26, he published an influential article, The Maths Behind the Contagion, in Italian newspaper Corriere della Sera. It advanced public understanding of why people needed to change their behaviour. And, although normally a slow writer, he says he felt “a constant need to write, to explain in rational terms what we’re going through”. Here, written in Rome between February 29 and March 4, is the result — a short book, How Contagion Works, part analysis, part journal, perhaps the first from the new world we all share. It is modest, lucid, calm, informed, directly helpful in trying to think about where we are now. Read more Books to read to get you through the Coronavirus pandemic In maths he trusts. Giordano is, he admits, a maths nerd and “epidemics are mathematical emergencies, first and foremost”. He explains with clarity that “the entire human species, in the eyes of the virus, falls into one of three categories: the susceptible, those it can still infect; the infected, those it already has; the recovered, those it can no longer infect. Susceptible, infected, recovered: SIR.” At the time he was writing, 40,000 around the world were infected, a slightly higher number recovered. The susceptible, though, were and are “7.5 billion, give or take a handful”. The speed of contagion depends on a number too, “the hidden heart of each epidemic”, noted with the symbol R0, pronounced “r-nought” — the number of susceptibles each infected causes to contract the virus. For Covid-19, the figure seems to be about 2.5. Any figure higher than 1 results in an epidemic. Only if it is less than 1 can the spread be halted. “Lowering R0 is the mathematical reason behind our self-sacrifice,” Giordano says: the self-isolation, the lockdown, all the loss and loneliness of that. “In times of contagion, what we do or don’t do is no longer just about us,” he says. Formula for contagion: Bondi Beach in Sydney was packed on March 20, despite a government ban on mass gatherings (Getty Images) We live in a globalised, connected world. “The simultaneous movement of 7.5 billion people, that is the coronavirus transport system.” He urges us to think of the ultra-susceptibles as not just the elderly or those with underlying health conditions but the poor in countries with no health infrastructure. “Community, in the contagion, is the entirety of the human species.” He also widens out the argument to tell us that we are ourselves to blame for the contagion because of our aggressive behaviour towards the environment (climate change, deforestation, urbanisation, extinction of species, intensive farming), bringing us into contact with pathogens which were until then confined to their natural niches. “Viruses are among the many refugees of environmental destruction,” he states, and we are the perfect breeding ground for them, so numerous, so susceptible, so connected, travelling so much. There will be other outbreaks. “The contagion is an invitation to think. And quarantine is the opportunity to do so,” he urges. “This is the time of anomaly; we need to learn to live with it, in it.” Yet, he admits, he cannot see beyond the crisis either. “What will happen after is a thought too complex for me; I can’t grasp it, I give up every time I try.” Unexpectedly he closes in exhortation, citing Psalm 90, verse 12: “Teach us to number our days, that we may gain a heart of wisdom.” He says: “Maybe it comes to mind because all we can focus on during this epidemic is numbers.” But he also observes that the psalm is telling us to number our days so that we may give value to them all, even these days, “in this painful interval”. The literature of the time after begins here. How Contagion Works: Science, Awareness and Community in Times of Global Crises by Paolo Giordano, trans Alex Valente​ (ebook £1.99, audio download £3.99, Weidenfeld & Nicolson pb April 26, £2.99), buy it here. More about: | Books | Book Reviews | Coronavirus | covid-19 Reuse content