A quarter of people with cold-like symptoms could have coronavirus and those with symptoms to stay at home, according to a British scientist.
Prof Tim Spector said many people were failing to self-isolate or get tested in the mistaken belief that they had the common cold.
The professor of genetic epidemiology at King’s College London said the UK should be “much more open-minded about who we are testing” and “get more people to isolate at least for a few days with cold-like symptoms”.
“At the moment, we’re estimating that somewhere between one in three and one in four colds are actually due to Covid,” he told Times Radio.
“And so that’s quite a high rate of people that are currently not even bothered to get a lateral flow test, or getting a PCR test, going to parties and spreading it around.
“So if that transfers to Omicron then we’re going to be compiling that problem much faster than we would need to.”
Anyone who feels unwell should stay away from the office or Christmas parties, he said, especially during the first few days of infection when they are at their most contagious.
“We want to tell people that if you don’t feel well that day, don’t go out, don’t go to work, work from home, because the start of that sniffle, the start of that sore throat, that headache could be a mild dose of Covid that is just breaking through your vaccine," Prof Spector said.
“So I think everyone needs to be much more aware of a whole range of symptoms and not wait for the loss of smell or taste which may never come, not wait for fever, not wait for that persistent cough.”
The warning came as authorities in England are attempting to stem the spread of the new Omicron variant by introducing PCR testing for travellers and hotel quarantine for those arriving from red list countries.
On Monday, UK Prime Minister Boris Johnson refused to rule out further restrictions over the Christmas period as he said new measures at curbing international travel were the right thing to do.
“I don’t think we need to change the overall guidance and advice we’re giving about Omicron in this country," he said.
"We’re still waiting to see exactly how dangerous it is, what sort of effect it has in terms of deaths and hospital admissions.”