A flood of new research suggests that far more people have had the coronavirus without any symptoms, fueling hope that it will turn out to be much less lethal than originally feared.

While that’s clearly good news, it also means it’s impossible to know who around you may be contagious. That complicates decisions about returning to work, school and normal life.

The head of the US Centers for Disease Control and Prevention (CDC) says 25 per cent of infected people might not have symptoms. The vice chairman of the Joint Chiefs of Staff, Gen John Hyten, thinks it may be as high as 60pc to 70pc among military personnel.

None of these numbers can be fully trusted because they’re based on flawed and inadequate testing, said Dr Michael Mina of Harvard’s School of Public Health.

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