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A trial is under way to test waste water for signs of Covid-19 in a bid to help pinpoint local spikes of the virus.

The samples are being taken at sewage treatment works in each of Scotland's 14 NHS health board areas.

They are then tested for fragments of Covid-19 in ribonucleic acid (RNA) which is produced by the body.

If successful, the results could be used by government ministers as part of their response to the pandemic.

The Scottish Environment Protection Agency (Sepa) said it was one of the first agencies in Europe to carry out this type of work.

'Early stages'

The samples will be taken at Scottish Water sites and tested by Sepa using methods developed by scientists at the Roslin Institute in Edinburgh.

Sepa chief executive, Terry A'Hearn, said the body was "in the early stages of this exploratory work".

"Our expertise in designing and implementing monitoring networks, coupled with our scientific capabilities, meant that we were able to get up and running quickly with the support of our partners," he said.

"Our hope is that our analysis could provide useful data in Scotland's efforts to trace the virus.

"However, we first have to understand what the samples are telling us and that's the important work our experts, alongside Health Protection Scotland, The Roslin Institute and others in the scientific community are embarking on now."

Useful indication

Sepa is keen to stress that there is no evidence that the fragments found in waste water are infectious.

There is no evidence to suggest that coronavirus can be transmitted through the sewage network.

But the amount of RNA present provides a useful indication of how many people have the condition.

Sepa says up to a half of the population will be represented in the sampling trial.

Dr Alexander Corbishley of the University of Edinburgh's Roslin Institute, said: "Detecting viral genetic material in waste water is relatively easy, however the challenge is accurately measuring how much genetic material is present and relating that to disease levels in the community."

Analysis by Kenneth Macdonald, ���˿��� Scotland science correspondent

This could be a powerful weapon against the pandemic - if researchers can establish how levels of RNA in waste water relate to how widespread Covid-19 is in the community.

And it highlights the huge advantage we have over the virus: we're smarter than it.

It's tempting to attribute human characteristics to it, to describe it as being clever or cunning, or to say that it wants to use our cells to reproduce.

But it doesn't want anything. It can't think. It's debatable whether the virus is even alive.

It's just a tiny scrap of genetic material that got lucky.

With lockdowns and all their associated hygiene measures, better treatments and perhaps vaccines, that means humankind has the chance to outthink it.