Are airplane toilets key to predicting the next pandemic?
International travel may never feel quite the same again. Scientists have taken to testing the sewage collected during cross-border flights in a bid to stop the next pandemic.
Across the globe, major airports are intercepting and analysing the waste from planes to provide a “true early warning” of any dangerous new arrivals.
Covid is just one of many pathogens including polio, Ebola and yellow fever that are passed through the body and can be detected in airline sewage, whether it be business class or economy.
Among the early adopters is Thailand, just a three-and-a-half-hour flight from Wuhan and where the first Covid-19 case outside China was detected on January 13, 2020.
Then, the Thai public health authorities had only temperature checks at airports to rely on. Now their surveillance programmes have shifted to examine passenger waste.
“We got the idea from our quarantine centres and hotels during the pandemic,” said Dr Rome Buathong, director of international communicable disease control at the Ministry of Public Health’s port and quarantine unit.
“We thought, if it works there, why don’t we test the material from aircrafts? People on long-haul flights have to go to the toilet”.
Everyday members of his team don hazmat suits and carefully collect samples from the hundreds of long-haul flights that arrive at Bangkok’s busy Suvarnabhumi airport.
The samples are analysed in a small lab inside the airport for diseases including Covid, yellow fever, west nile virus and – most recently – polio.
It is surprising, and perhaps a measure of the damage the pandemic has done, that monitoring international airline waste has only recently started.
As far back as the 1940s, scientists in the US first proposed tracking polio in urban sewage, and in the years since it’s become an essential monitoring tool.
Not only do many viruses and bacteria survive for days in human waste, but they leave a trace even after they’ve died.
Covid is among the pathogens detectable in sewage, and during the pandemic countries from the UK to India launched monitoring programmes.
In many cases, results acted as an early warning system, alerting officials to new hotspots.
Yet testing transnational waste from aeroplane toilets is only just starting. Experts say it has the potential to be a “true early warning” system for future pandemics.
“[It] emerged from the Covid pandemic but has previously been discussed for monitoring antimicrobial resistance,” said Prof Kevin Thomas, director of the Queensland Alliance for Environmental Health Sciences at the University of Queensland.
Last year, Prof Thomas co-authored a Lancet report calling for the establishment of a global monitoring network to track “the threat of novel Sars-Cov-2 variants and future global health risks”.
This would involve a global network of strategic international airports across five continents. Genomic sequencing data collected from aeroplane waste would be combined with data on travel history, to track and model the global movement of viruses in real-time.
“Detecting ‘disease-x’ – an unknown pathogen – is feasibly possible but is not without its challenges,” Prof Thomas said. “The current and immediate future application will be for known entities.”
Conversations about how to establish such a network are ongoing, though there was plenty of interest at a conference in Frankfurt in November.
But in the meantime, feasibility studies have been conducted in the UK, while the European Commission issued “ad hoc guidance” for sampling aircraft wastewater in January 2023, and San Francisco International Airport became the first in America to adopt the surveillance technique last May.
In Thailand, a pilot monitoring waste in planes was launched in July 2022, when the country lifted requirements for incoming passengers to quarantine and test on arrival.
Scientists wanted a mechanism to continue scanning for new variants, so turned to long haul toilets. In a targeted approach, they took samples from select planes to get a sense of which Covid strains were entering Thailand.
“The idea is that if we detect new variants as they arrive, we can alert the authorities. This is a super important thing to know… as it informed our pandemic response,” said Dr Buathong.
He added that because the team is only able to gather samples from five to 10 flights per day, they targeted specific planes arriving from countries where concerning variants were known to be spreading.
By late 2022, the pilot had proved so effective that the unit decided to expand, taking in a range of viruses including polio.
This came amid mounting concerns about wild and vaccine-derived polio strains spreading in Afghanistan, Pakistan, Indonesia and parts of Africa.
“So we can look at asymptomatic carriers [of polio] and if we find it, we will ramp up surveillance inside the country,” said Dr Buathong.
He added that the team target different countries depending on external events. During Hajj pilgrimage last summer, for instance, they focused on looking for Mers and Covid among flights landing from Saudi Arabia.
“Mers is not yet spreading here, but through this programme we can know it is here before we see cases,” Dr Buathong said. “If it started to spread as a pandemic, we would know very rapidly.”
There are also concerns about yellow fever – the virus is not currently found in Southeast Asia, but the mosquito which spreads it is.
Sewage surveillance complements Thailand’s existing strategy, where arrivals from Latin America and Africa have to prove they have had a yellow fever vaccination.
But there are limits to these wastewater programmes. The most significant is toilet use – it only works when people actually go to the bathroom when on board, which makes the technique much more applicable to long haul flights.
It is also not possible to identify which individual was infected, and analysing samples can be expensive.
“[Health officials] may not be able to differentiate travellers with connecting flight itineraries, which may affect the ability to detect the origin of an outbreak,” added Prof Thomas. “[So there’s a] potential issue with carryover of a signal between flights.”
But for Dr Buathong, who led the team that identified the first Covid-19 case outside China, wastewater surveillance in planes is a crucial additional tool as countries race to better understand cross border disease transmission.
“I think doing this work is very important,” he said. “It is convenient to collect samples from wastewater rather than from passengers individually … and we’ve shown it works. It is an extra way to allow Thailand to detect threats.”
- The Telegraph
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