Wastewater from flights can help detect COVID-19 before passengers show symptoms

Researchers from The University of Queensland and Australia's national science agency CSIRO have found SARS-CoV-2 virus in wastewater samples from long haul flights of returning Aussies, proving they can detect it before passengers show symptoms.

The CSIRO and UQ scientists worked with Qantas to demonstrate that wastewater surveillance can provide valuable data for public health agencies and help improve confidence in Australia's safe reopening to the world.

CSIRO lead author Dr Warish Ahmed said as global travel returns, wastewater testing of flights can be an effective way to screen incoming passengers for COVID-19 at points of entry.

It provides an extra layer of data, if there is a possible lag in viral detection in deep nasal and throat samples and if passengers are yet to show symptoms.

The rapid on-site surveillance of wastewater at points of entry may be effective for detecting and monitoring other infectious agents that are circulating globally and provide alert to future pandemics."

Dr Warish Ahmed, CSIRO Lead Author

Co-author Professor Jochen Mueller from UQ's Queensland Alliance for Environmental Health Sciences said wastewater testing could be a useful additional tool.

"The paper recommends that wastewater surveillance be used as part of an efficient clinical surveillance and quarantine system – providing multiple lines of evidence of the COVID-19 infection status of passengers during international travel," Professor Mueller said.

"Wastewater surveillance from large transport vessels with their own sanitation systems significantly improves our ability to control the spread of infection from overseas travellers."

Published today in Environment International, the study analysed wastewater samples from 37 Australian Government repatriation flights from COVID-hotspots including India, France, UK, South Africa, Canada and Germany landing at Darwin International Airport between December 2020 and March this year.

The research found wastewater samples from 24 of the 37 repatriation flights (65 per cent) showed a positive signal for the virus that causes COVID-19 despite all passengers (except children under age five) testing negative to the virus 48 hours before boarding.

Infected people shed the virus in their faeces about two to five days before showing symptoms.

Traces of COVID can also be detected in wastewater from people who were previously infected, are still shedding the virus, but no longer infectious– although this is typically a weaker signal.

During 14 days of mandatory quarantine after arriving in Australia, clinical tests identified only 112 cases of COVID-19 among the 6570 passengers (1.7 per cent).

This was the first official study of wastewater from Australian repatriation flights returning from hot spots and the first time researchers have matched the plane wastewater testing with the follow-up clinical data testing of passengers in quarantine.