Samples of wastewater from the Paris sewage system have been showing traces of Covid-19 again since the end of June, having vanished when France imposed a lockdown, according to the head of the laboratory leading the research, Reuters reports.

Early studies by scientists in the Netherlands, France, Australia and elsewhere suggest sewage sampling for signs of the SARS-CoV-2 coronavirus could help estimate the number of infections in a geographic area, without having to test every person.

Read the full story here.