Wastewater from aircraft toilets could provide a critical warning system for the global spread of antimicrobial resistant (AMR) superbugs, a silent pandemic that threatens to kill more people than cancer by 2050.
A new study led by scientists from Australia’s national science agency CSIRO, in partnership with Xiamen University, the University of South Australia and Michigan Technological University, analysed lavatory wastewater from 44 international flights arriving in Australia from nine countries.
The team detected nine high-priority pathogens and superbugs, including some that are acquired in hospitals and resistant to multiple drugs. The researchers used advanced molecular techniques to analyse the superbugs’ genetic signatures and antibiotic resistance genes (ARG) profiles.
Five of the nine superbugs were found in all 44 flight samples, while a gene conferring resistance to last-resort antibiotics was detected on 17 flights. Notably, this gene was absent in Australia’s urban wastewater during the same period, suggesting its likely introduction through international travel.
The findings, published in Microbiology Spectrum, confirms that aircraft wastewater is a viable tool for global AMR surveillance, according to senior author Dr Warish Ahmed, a principal research scientist from CSIRO.
“Aircraft wastewater captures microbial signatures from passengers across different continents, offering a non-invasive, cost-effective way to monitor threats like AMR,” Dr Ahmed says.
The wastewater samples revealed significant geographic variations, according to co-author UniSA microbiologist Professor Nicholas Ashbolt, from the Future Industries Institute.
“Flights from Asia, particularly India, showed higher concentrations of antibiotic resistance genes, compared to flights from Europe and the UK,” Prof Ashbolt says.
Of the 44 international flights, 18 originated from India, 14 from the United Kingdom, six flights from Germany and the remainder were single flights from France, UAE, Türkiye, South Africa, Japan and Indonesia.
Lead author Dr Yawen Liu, a visiting scientist at CSIRO from Xiamen University in China, says these disparities could reflect differences in antibiotic use, water sanitation, population density and public health policies across regions.
The study also tested whether disinfectants used in aircraft toilets degrade genetic material. The results showed that nucleic acids remained stable for up to 24 hours, even in the presence of strong disinfectants, confirming the reliability of aircraft wastewater for surveillance purposes.
“International travel is one of the major drivers of AMR spread,” says Dr Liu. “By monitoring aircraft wastewater, we can potentially detect and track antibiotic resistance genes before they become established in local environments.”
Infectious diseases such as tuberculosis, influenza and SARS-CoV-2 are all known to have been spread by air travel. Multi-layered control strategies have been trialled to reduce their transmission, including travel restrictions, individual passenger screening, and quarantine.
The samples used in the study were collected during the COVID-19 pandemic repatriation flights, which may have influenced passenger demographics. However, the authors say that the approach can be adapted to routine international travel.
“With AMR projected to cause more than 39 million deaths globally by 2050, the need for innovative surveillance tools is urgent,” Prof Ashbolt says.
“Aircraft wastewater monitoring could complement existing public health systems, providing early warnings of emerging superbug threats.”
“This is a proof-of-concept with real-world potential,” says Dr Ahmed. “We now have the tools to turn aircraft toilets into an early-warning disease system to better manage public health.”
