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CSIRO testing wastewater from long-haul flights

Australia’s national science agency, the CSIRO, has analysed wastewater samples from long haul flights of returning Aussies which prove signals of the SARS-CoV-2 virus can be detected even before passengers show symptoms.

The research from CSIRO scientists, working with Qantas and The University of Queensland, demonstrates 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,” Dr Ahmed said.

“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.”

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Professor Jochen Mueller from UQ’s Queensland Alliance for Environmental Health Sciences and co-author on the research said wastewater testing could be a useful additional tool.

“The paper recommends that wastewater surveillance should 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,” 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 in Environment International, the study analysed wastewater samples from lavatories of 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, still shedding the virus, but are no longer infectious to others (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).

There was 87.5 per cent agreement between the positive detections by surveillance of the wastewater (i.e., detection of SARS-CoV-2 RNA) and the subsequent clinical detections made during the passengers quarantine.

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.

For the study, CSIRO undertook the wastewater analyses, and much of the data analysis with input on from University of Notre Dame, USA. Qantas designed the sampling trap with input from The University of Queensland and both organizations were involved in study design and wastewater sampling.

The participants of this study were quarantined at the Howard Springs Quarantine Facility in the Northern Territory.

The latest study builds on work from an earlier paper published in the Journal of Travel Medicine in July 2020, which detected fragments of the SARS-CoV-2 virus in aircraft and cruise ships.

According to the latest paper, surveillance of wastewater from aircraft and cruise ships offers a convenient and cost-effective means of monitoring infectious agents that could be globally scaled to detect and manage the importation of disease.