Was Covid with us long before anyone realised?

One of the mysteries of the Covid-19 crisis is how the disease seemed to bubble up out of nowhere in Italy at the end of February – at a time when it seemed to be under control in China. In spite of local quarantines and the isolation of individual patients, the epidemic quickly took hold. We have subsequently had reports of patients infected all over Europe who were possibly infected in mid-January. 

But now a study has emerged that suggests the disease was already circulating in Northern Italy before Christmas. A team from the Institute for Public Health in Rome studied 40 wastewater samples collected from sewage works near Milan, Turin and Bologna between October last year and February this year. In 15 of them, they detected the presence of Sars-CoV-2, the virus that causes Covid-19. Eight of these positive samples came from before Italy’s first native case of Covid-19 was diagnosed on 21 February.