From the airplane waste, the Danish researchers could identify regional patterns. Genes for antimicrobial resistance, for example, were more abundant in samples from South Asia than North America. They found differences in specific bacteria, too: Salmonella enterica, which can cause diarrhea, was more common in South Asian samples while Clostridium difficile, the bacteria behind a difficult-to-treat hospital-acquired infection that often follows a course of antibiotics, was most common in North American samples. “It was good that we didn’t have really nasty things like anthrax,” says Thomas Sicheritz-Pontén, a molecular biologist at Technical University of Denmark who co-authored the paper.

Those really nasty things are out there, though, and Sicheritz-Pontén says DNA analysis of airplane poop could help flush out signs of emerging outbreaks. If the prevalence of certain bacteria coming from say, South America, suddenly shoots up 100 times, that’s an alarm bell. In contrast, the old-fashioned methods of surveillance—like tracking doctors’ reports—are slow and reactive. “When you’ve detected it, you already have an epidemic,” says Sicheritz-Pontén. The study is a proof of concept that bacterial genes of interest are detectable.