Hunting for viruses in sewers to anticipate epidemics

Epidemics can be anticipated: you can know when a virus is about to break out and spread, you can take countermeasures in time. Even two months earlier. How is it possible? An Italian study explains this, emphasizing the fact that viruses in the expansion phase, at a given historical moment, which could also coincide with the winter that is about to begin, can be intercepted before they strike by examining waste water.