In Iceland, nearly half of people with COVID-19 had no symptoms when they were swabbed for a scientific study. In the United States, preliminary results from a new antibody survey suggests as many as one in five New Yorkers may have been exposed to the novel coronavirus. And in the waters off the coast of Guam, more than 850 sailors on a navy warship have been infected in a massive outbreak — with roughly half reporting no symptoms when they were tested. In the early days of COVID, experts were skeptical of initial reports of asymptomatic cases, which weren’t thought to play a significant role in spreading the disease. But four months on, there is mounting evidence that “silent spreaders” are a major driver of the pandemic, with top scientists now speculating they could comprise between 25 and 50 per cent of all cases.