• About 144,000 people a day are catching it and then feeling unwell. For most, Covid is a mild disease. Some get no symptoms at all.
• If you have cold-like symptoms, take a Covid test, says lead scientist Prof Tim Spector.
If you have a sore throat, runny nose, and a headache there is a good chance it will be Covid, warn UK researchers.
The Zoe Covid study team has been tracking the pandemic using feedback from the general public and estimates half of the people with cold-like symptoms actually have Covid.
They describe an "explosion" of Covid cases over the last week, driven by the new Omicron variant.
About 144,000 people a day are catching it and then feeling unwell.
For most, Covid is a mild disease. Some get no symptoms at all.
But it can still cause very serious illness in some people, including those who have not been vaccinated.
If you have cold-like symptoms, take a Covid test, says lead scientist Prof Tim Spector.
"The number of new symptomatic cases has exploded over the last week," he said.
"For most people, an Omicron positive case will feel much more like the common cold, starting with a sore throat, runny nose, and a headache. You only need to ask a friend who has recently tested positive to find this out.
"We need to change public messaging urgently to save lives."
The UK reported 106,122 new Covid cases on Wednesday - exceeding 100,000 on a single day for the first time.
With infections doubling every two to three days, experts say, health officials are concerned about the pressure this could put on the NHS.
Preliminary studies suggest the Omicron coronavirus variant is milder, with fewer people getting severely ill than with other variants.
But a massive wave of infections would still mean many people needing hospital care, as well as lots of doctors and nurses being off sick with Covid.
People are being advised to do rapid Covid tests before meeting up with friends and family at Christmas.
Lateral flow tests help to find cases in people who may have no symptoms but are still infectious, meaning they can give the virus to others.