By sampling sewage across greater Paris for more than 1 month, researchers have detected a rise and fall in novel coronavirus concentrations that correspond to the shape of the COVID-19 outbreak in the region, where a lockdown is now suppressing spread of the disease. Although several research groups have reported detecting coronavirus in wastewater, the researchers say the new study is the first to show that the technique can pick up a sharp rise in viral concentrations in sewage before cases explode in the clinic. That points to its potential as a cheap, noninvasive tool to warn against outbreaks, they say.
“This visibility is also going to help us predict a second wave of outbreaks,” says Sébastien Wurtzer, a virologist at Eau de Paris, the city’s public water utility. Wurtzer and his colleagues posted the study, which has not been peer-reviewed, on the preprint repository medRxiv on 17 April.
Sewers offer near–real-time outbreak data, because they constantly collect feces and urine that can contain coronavirus shed by infected humans. (Once excreted from the body, the virus degrades quickly, although scientists have found limited instances of infectious virus in fecal matter.) Polymerase chain reaction testing identifies fragments of RNA from SARS-CoV-2, the virus that causes COVID-19. Higher concentrations of virus in the wastewater corresponds to higher numbers of infected people who contribute to the sewer system.