Is it safe to come out of the lockdown? Check the sewer

Wastewater could provide early, painless data about the rise or fall of coronavirus levels

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,