RE: The New Statesman on UK sewage testing30 Mar 2021 21:34
Part 2
cute-sounding pepper mild mottle virus – as a benchmark, giving us an indirect flag of how much faeces is present at any given time. Analysts can then adjust their RNA analysis to match.
Contrary to some earlier, overblown claims, sewage rates don’t correlate perfectly with disease: the overall correlation seems to be somewhere in the region of 0.4, on a scale of -1.0 to 1.0. Not super-strong, but far better than nothing. And although more works needs to be done (there are calls to make more of the data available for research), most scientists think wastewater testing will be an important part of the tool-kit for monitoring Covid in future.
This comes with some big advantages. Although the wastewater analysis isn’t accurate enough to tell us the prevalence of Covid in any given area (it’s more about the change over time than the level of infection), it could serve as a non-invasive early-warning system, telling us where we should be aiming our testing, messaging and restrictions. It’s particularly useful for schools as children are too young to receive the current vaccines. It could help us to spot the appearance of new variants of the virus. And it could partly address one of the perennial features of the Covid pandemic, inequality, by drawing our attention to outbreaks in areas with lower uptake of testing and vaccination.
Expect to hear a lot more about wastewater Covid testing in the coming months. Although the government hasn’t yet made good on its plans to add the data to the official UK government's coronavirus dashboard, you can see similar numbers from Scotland, the Netherlands, Canada and many cities and regions worldwide.
Maybe those who know their scientific history could have predicted – even without psychic powers or horoscopes – that sewage-based testing would end up being important. Not only has it shown promise for tracking other diseases in the past, but the very foundation of the science of epidemiology lies in wastewater. When John Snow mapped out a cholera epidemic in 1850s London, it dawned on him that the disease was in the water, which led to his disabling of the Broad Street Pump in Soho, halting the epidemic in its tracks.
It won’t be as simple for Covid-19, which of course isn’t spread (much) by contaminated water. But it’s there all the same, and – weird and perhaps unpleasant as it may sound – we’re now using that knowledge to our advantage.
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