RE: Happy face, Happy face !4 Mar 2022 21:07
Barry Slade has an easy affinity for effluent. “After 33 years it’s normal to me,” he says, casually cradling two plastic bottles of murky brown water in the way a tennis player would hold some Evian.
When sewers need sampling, Slade is the man with the bucket and disposable gloves. “I’ve found everything,” he says, shouting over the rushing sound of a river of effluent. “And nothing frightens me any more”. Although, for the past 18 months he has indeed been finding something new in his samples: coronavirus.
Slade is part of the latest arm of the UK Health Security Agency’s coronavirus surveillance system, an arm that it is hoped could soon be expanded to be a permanent feature of public health, monitoring the spread of disease in the population. What that means, in practice, is that three times a week Slade or a colleague goes Covid dipping in Reading’s sewers.
Over the past two years, in over 400 sites across the country, Britain has built from scratch one of the most extensive wastewater sampling operations in the world. The justification for this is simple. It doesn’t rely on people volunteering to give a sample. “We all poo somewhere,” says Andrew Engeli, of the UKHSA.
If you look at national testing data, you are just seeing the Covid-positive cases of those who chose to get tested. If you look at representative samples, like the Office for National Statistics’ Infection Survey, which involves thousands of tests taken at houses across the country every day, you are getting gold-standard surveillance, but at a phenomenal cost.
Defecation, though, is the great leveller. “The great advantage of wastewater,” says Engeli, “is it knows no community biases, it knows no behavioural biases.”
Already, the system is being used to monitor variants of concern and predict ventilator use. It has been shown in several studies that rising coronavirus prevalence in wastewater is an indication of rising coronavirus prevalence in hospital ten days later.Soon, it could well be adapted to other viruses such as flu, RSV and norovirus to become yet another Covid legacy that ends up a permanent fixture of UK public health surveillance. But the process, and the interpretation of what is found, has been far from simple.
Perhaps two hours before Slade lifted a manhole and dropped a bucket, someone in Reading went to the lavatory. That person had Covid.
Their waste was flushed into the local sewer, along with the genetic fragments of dead virus, and travelled into increasingly larger sewers. Buffeted and pounded, sloshed and splashed, the viral RNA mixed with the sewage, and viral fragments, of thousands of other Reading residents. Until, flowing at 1,000 litres per second, it made it to the Reading sewage treatment works, and Slade’s bucket.
When the contents of that bucket are sent to the laboratory, fragments of the RNA from their infection will mingle with those from other Reading infections and be amplified and picked up together.
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