The UK has built an end-to-end wastewater system across 31 sites, testing for 12 priority pathogens that could cause problems to public health. Over the next year, ministers want to expand environmental surveillance across sewers, hospitals and transport settings. A separate pandemic preparedness plan says the UK Health Security Agency (UKHSA) will explore sampling aircraft wastewater to detect diseases arriving in Britain.
Wastewater as an early warning system
“Wastewater tells no lies — everything we do in society is reflected in the wastewater,” says Davey Jones, professor of environmental science and public health at Bangor University. The Government’s UK Biological Security Strategy, published in July, sets out plans to connect different forms of disease surveillance, while UKHSA is spending £1.3 million testing whether wastewater can reveal genetic traces of pathogens including Mpox and West Nile virus.
Already, wastewater is checked for the presence of polio. Earlier this year, the tracking of wastewater found two indications of vaccine-derived poliovirus in sewage samples taken from London. That was important because Australia — with whom London has regular flight connections — had a small spate of similar results. But indications in such small numbers in London are routine, and didn’t require any public health intervention, authorities said.
Constructing a viral family tree
It was a very different situation in 2022, when genetically linked detections occurring time and time again suggested there was person-to-person transmission in north and east London. That outbreak prompted a vaccination campaign within areas of the capital. Polio is a special case because Britain has monitored sewage for it routinely since 2014. But it also shows that it’s possible for scientists to separate nascent outbreaks from the biological background noise.
“You have the pathogen in the sample, so you can sequence it,” says Nicholas Grassly, professor of infectious disease and vaccine epidemiology at Imperial College London. With more than one detection, researchers can construct a viral family tree, he explains, helping them understand “where it’s come from”. But it’s harder than it first seems. “Picking up a signal is extremely difficult if you don’t know what you’re looking for,” says Barbara Kasprzyk-Hordern, who leads the University of Bath’s Centre of Excellence in Water-Based Early-Warning Systems for Health Protection.
That means that wastewater analysis is just one weapon in the arsenal that needs to be used to tackle potential problems before they arise. While wastewater can indicate where officials should look, doctors and laboratories need to establish whether people are becoming ill and what treatment is needed. Grassly describes wastewater as “a free biological sample from hundreds of thousands of individuals”, one that can indicate how widespread an infection is without requiring each person to come forward for testing. The same sample can also be searched for several pathogens at once. That means health authorities can track common illnesses such as Covid, flu, respiratory syncytial virus (RSV), measles and polio while looking for rarer virus signatures in the background.
A signal from the airplane loo
Aircraft toilets could add another layer. In a 2022 UK study, researchers sampled sewage from terminals and 32 aircraft at Heathrow, Bristol and Edinburgh airports. At the peak of the pandemic, 93 per cent of aircraft samples contained SARS-CoV-2 — the virus that caused Covid. The Government now wants to evaluate whether similar methods could flag imported diseases without swabbing passengers individually — helping scale up detection of potential problems before they arise.
The ability of wastewater to survey whole populations without identifying individuals is a massive advantage and can help identify from where outbreaks occurred, and help snub them out before they become significant. “We never know who is ill,” says Kasprzyk-Hordern. “But we know how communities were exposed.” Once signs that something is wrong appears in wastewater, conventional testing can be used to find out whether people are infected and whether an intervention is required.
Grassly points out that there is another limitation. Finding a virus at Heathrow may buy Britain several days or perhaps a week compared with hospital detection — but it also means the pathogen is already travelling internationally. His Wastewater Surveillance for Pandemic Prevention network is therefore looking further upstream, in communities in Africa and South-east Asia where animal viruses repeatedly spill into people.
Those small spillovers are “the sparks of the fire”, Grassly says. Detecting them early could allow safer market practices or interventions in livestock before an outbreak becomes a global emergency. “The biggest benefit will be when we align all the pieces of information together,” says Kasprzyk-Hordern, including what is happening at the clinical, community and environmental levels. “We’re not there yet.” But with work, it’s possible to be. As Grassly puts it, “prevention is going to be much easier than being responsive”.
