Typical signs of Covid-19 have changed over the course of the pandemic as the virus has evolved, new variants have emerged and more people have been vaccinated.
The original trio of symptoms to look out for at the start of the pandemic - fever, new and continuous cough and loss or change of taste or smell - no longer appear to be the main symptoms for either the Delta or Omicron variants.
According to Professor Tim Spector, lead scientist on the Zoe Covid study, "cold-like symptoms appear to be the predominant feature of Omicron".
We look at how to tell the difference between a cold and Covid and when to get tested.
There are now more than 20 symptoms of Covid-19 which have been reported to the ZOE Covid Study app, ranging from coughs and runny noses to skin rashes and diarrhoea.
The current top five are: a runny nose, headache, fatigue, sneezing and sore throat.
The Omicron variant has also been associated with a scratchy throat, aches and pains, and no loss of taste or smell in early reports from South Africa, where the variant was first identified.
Many of the symptoms of Covid-19 are now the same as a regular cold, especially for people who have received two doses of the vaccine, which makes it harder to tell the difference.
Data from the ZOE study has, however, shown loss of smell or taste can still be an important predictor of testing positive for Covid-19 rather than a regular cold, whether vaccinated or not.
The most common symptoms of Covid-19 for fully vaccinated people, from September, were: runny nose, headache, sneezing, sore throat and loss of smell.
Among unvaccinated people, it was: headache, runny nose, sore throat, fever and persistent cough.
The NHS recommends you should get a PCR test if you have any of the following symptoms: high temperature, new continuous cough or loss of taste or sense of smell.
The ZOE Covid Study app if you have any of the common Covid symptoms you should stay home and get tested, even if you have been vaccinated.
If you have a positive result from a lateral flow test, then a PCR test should be done.
If you have a negative result from a lateral flow but symptoms persist, then a PCR tst should be done.
And if you have been in close contact with someone who has tested positive for Covid-19 and you are not fully vaccinated, you should do a PCR test.