Small traces of many pathogens, such as viruses we may be infected with, are excreted when we go to the toilet. Ultimately, these agents find their way to municipal wastewater treatment plants where sewage samples can be taken and the levels of these pathogens measured.
This field of science is called wastewater-based epidemiology and it may be a way to track the spread of COVID across the world via airports. It’s already a powerful tool to monitor the levels of infectious diseases circulating in a community. It’s also relatively simple, inexpensive, and, most importantly, provides a snapshot of the health of a whole community (not only those people who seek medical help).
