ONLY around half of coronavirus cases in the UK are being picked up by health authorities, according to a pandemics expert.
Mark Woolhouse, professor of infectious disease epidemiology at the University of Edinburgh, believes attempts to control the virus are being done "with one hand behind our back".
The scientist sits on a sub-group of Sage and is a member of the Scottish Government's Covid-19 advisory group.
He said the mass testing scheme which began in Liverpool is an attempt combat the problem.
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From Friday anyone in the city can be tested – repeatedly – for coronavirus regardless of whether they have symptoms.
Speaking on the BBC Scotland's Seven Days programme, Woolhouse explained: "The problem that testing pilot scheme in Liverpool is trying to solve is that we're still not finding about half of the Covid cases in Scotland or in the UK more generally.
"That's a very high proportion."
He added: "It's probably partly because many of them are asymptomatic or so mildly infected they don't recognise the symptoms, partly because people do have symptoms but actually genuinely aren't recognising them as Covid - I've heard a few cases of that in the last week – and also the possibility that some people are having symptoms and actually ignoring them, perhaps because they don't want to go into self-isolation.
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"Whatever the reason, those missed 50% of cases - it's like trying to control the epidemic with one hand tied behind our back. We can't do it effectively if those cases are not also being self isolated and their contacts traced. It's going to make it much more difficult.
"The idea of Liverpool is to try and find these cases and hopefully ... persuade them to self-isolate."