Half of people with cold-like symptoms will have COVID-19, a UK study suggests.
Headache, fatigue, runny nose, sore throat and sneezing are the top symptoms reported on the ZOE app.
It's "virtually impossible" to tell between a cold and COVID-19 without a test, epidemiologist Tim Spector, the study lead, said.
One in two people with new cold-like symptoms will have COVID-19 rather than the common cold, new data from the Zoe symptom tracker app suggests.
Tim Spector, an epidemiologist and the study's lead author, said in a press release on Thursday that for most people, getting infected with Omicron will feel "much more like the common cold, starting with a sore throat, runny nose and a headache", rather than fevers, continuous cough, loss of taste or smell.
To get to the 50% figure, Spector and his team compared the number of new cases of a cold-like illness to the number of new cases of COVID-19 confirmed by a lateral flow or lab test.
"We need to change public messaging urgently to save lives as half of people with cold-like symptoms now have COVID-19," Spector said.
"It's virtually impossible" to tell between a cough and COVID-19 unless you get tested, he said.
Scientists are still racing to find out if the Omicron variant, which is fast-spreading in several countries including the UK, US, Denmark and South Africa, does indeed cause milder illness than Delta. In his statement, Spector said it is still too early to gauge Omicron's severity from the data we have - a perspective shared by many other experts, as Insider reported today.
According to Spector's findings, people with Omicron reporting symptoms on the Zoe app were less likely to have five or more symptoms than those with Delta.
He has found at least 20 common symptoms currently being self-reported by Zoe's 850,000 weekly users.The top five are headache, fatigue, runny nose, sore throat and sneezing - similar to the symptoms from the Delta variant.
"Waiting for those symptoms to occur is not a good way to see if you've been infected, or if you should get a test," he said.