Wastewater research isn't for the squeamish, but it can get to the bottom of questions about such things as the effectiveness of COVID-19 air travel restrictions.
Tests of toilet tank water from flights entering the United Kingdom helped Welsh scientists determine that steps meant to keep the virus from traveling among countries appear to have failed.
"Despite all the intervention measures that the U.K. had in place to try to stop people with the illness getting on flights to the U.K., almost every single plane we tested contained the virus, and most of the terminal sewers, too," said researcher Davey Jones, a professor in the School of Natural Sciences at Bangor University in Wales.
"That might have been because people developed symptoms after testing negative; or were evading the system, or for some other reason," Jones said in a university news release. "But it showed that there was essentially a failure of border control in terms of COVID surveillance."
For their study, the researchers tested the toilet tank water taken from long- and short-haul flights entering Britain at three airports -- Heathrow, Edinburgh and Bristol -- between March 8 and March 31, 2022.
They also collected samples from sewers connected to arrival halls in the airport terminals and from a nearby wastewater treatment plant.
During those three weeks, almost all planes had SARS-CoV-2 in their wastewater samples. The virus was also found in wastewater at arrival terminals.
During the study period, on March 18, 2022, a requirement that unvaccinated passengers get tested for COVID before departure and two days after arrival was lifted. Researchers saw little difference in the wastewater before and after that date.
In earlier study by the same team, 23% of respondents in a poll of 2,000 adults said they had boarded a flight to the United Kingdom while feeling ill.
About 13% of people taking a short-haul flight said they would be likely to have a bowel movement on the plane. About 36% said they would do so on a longer flight.
Researchers estimated that wastewater sampling at airports could capture about 8% to 14% of COVID cases entering the United Kingdom through air travel.
This sampling could be part of future infectious disease surveillance system for the United Kingdom, they said. It might also detect other infections, such as norovirus or enterovirus.
"This is about getting an overall picture to help U.K. health systems to be prepared, or, if possible, have an advance warning, of emerging diseases," microbiologist Kata Farkas said in the release. "It wouldn't be feasible to test every flight arriving but taking wastewater from arrivals at a single airport terminal used for long-haul arrivals may provide an estimate of diseases entering the country."
Farkas said authorities have no idea how many people enter the country carrying different diseases, partly because no one wants to be tested on the spot.
"Wastewater monitoring gives us a snapshot of the infectious diseases passengers may carry upon arrival," she said.
The findings were published Jan. 19 in PLOS Global Public Health.
The U.S. Centers for Disease Control and Prevention has more on travel and COVID-19.
SOURCE: Bangor University, news release, Jan. 19, 2023