About half of all positive Covid-19 cases in the UK are not being detected, an expert has said.
Mark Woolhouse, professor of infectious disease epidemiology at the University of Edinburgh, said these infections meant the country’s efforts to control the virus were being carried out "with one hand behind our back".
Prof Woolhouse sits on a sub-group of the Scientific Advisory Group for Emergencies (Sage) is a member of the Scottish government's Covid-19 advisory panel.
He said the mass testing project which began in Liverpool was an attempt combat the problem.
On Friday, thousands of people queued up outside six new testing centres in the city under a pilot for which hundreds of soldiers have been drafted in.
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, Prof Woolhouse said: "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.
"Whatever the reason, those missed 50 per cent 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."
It comes as Wales 17-day ‘firebreak’ lockdown ended today and a new set of regulations came into force.
Wales' chief medical officer Dr Frank Atherton said there were some “early signs of stability.”
Speaking on BBC Radio 4's Today programme, he added: "We are coming out of the firebreak arrangements today.
"We always recognised that there would be a lag in terms of the indicators we look at as to how successful we have been.
"But we are seeing some early signs of stability and we are seeing that in mobility data, so we recognise that the people of Wales have been travelling significantly less during the firebreak, and we are starting to see that in some of the testing rates."
Join our new commenting forum
Join thought-provoking conversations, follow other Independent readers and see their replies