How safe are we? Check the sewer

The world is eager to come out of lockdown. But if countries simply return to business as usual, new outbreaks of Covid-19 will follow. The only solution that public health experts see is to keep careful track of the coronavirus and clamp down on new flare-ups. The trouble is that the most obvious way to monitor the virus — testing person by person — has already proved to be a huge, expensive challenge.

Experts say we’re nowhere near the scale we need to get a good picture of the pandemic. Now some scientists are looking for the virus not in our noses, blood or spit, but somewhere else: in our sewers.