Explained: How the UK is testing sewage to detect the presence of COVID-19

Over a year ago, researchers in Australia developed an early warning surveillance system to track the community transmission of COVID-19 by tracing the presence of the virus’s genes in raw sewage.

The UK government is expanding its testing of wastewater to detect the presence of coronavirus and its emerging variants.

According to the country’s Department of Health and Social Care, the testing has now been ramped up to cover about two-thirds of the population. A new laboratory situated in Exeter, which will analyse the samples of wastewater, has now become one of the biggest such labs in the world.

Why test wastewater?

Over a year ago, researchers in Australia developed an early warning surveillance system to track the community transmission of COVID-19 by tracing the presence of the virus’s genes in raw sewage. This was possible because some infected individuals may shed the virus in their stool or urine.

This method is especially useful in identifying the scale of spread of the disease in a community. By detecting and quantifying the amount of virus found in the samples gives an indication of how widespread the virus is in an area, information that can be used by decision-makers to put restrictions on movement for certain people or start testing in an area more aggressively. Even in areas where widespread testing may not be feasible, adopting this method can point out the efficacy of containment measures.

For instance, wastewater testing in the Luton Borough Council of England led to the understanding that the increase in cases was not a result of community transmission, but limited to person-to-person transmission.

Specifically, in the UK researchers are now looking at the spread of variants including the one first detected in South Africa and India.

How does wastewater testing work?

After wastewater samples are taken from about 500 locations across the country, they are sent to the laboratory at Exeter Science Park. Here, scientists test and analyse the water samples to quantify the amount of virus present in them. Further, some of these samples are sent to other laboratories where they are sequenced to identify variants.

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