The strain, which was first discovered by scientists in South Africa at the end of November, has been found to be more transmissible and evade vaccines more easily, helping it to spread quickly.
With infections soaring, the booster jab roll-out has been accelerated and new Covid restrictions have been introduced in Scotland, Wales and Northern Ireland – although England will remain under Plan B measures until at least the New Year.
What are the symptoms of the Omicron Covid variant?
According to the NHS, the main symptoms of Covid-19 remain as they have been for most of the pandemic:
- High temperature: This means you feel hot to touch on your chest or back (you do not need to measure your temperature).
- New, continuous cough: This is defined as coughing a lot for more than an hour, or three or more coughing episodes in 24 hours (if you usually have a cough, it may be worse than usual).
- Loss or change to your sense of smell or taste: This means you have noticed you cannot smell or taste anything, or things smell or taste different to normal.
However, leading health experts have warned that the official guidance is not extensive enough, and risk people spreading the Omicron variant unwittingly by dismissing them as signs of the common cold.
Professor Tim Spector, lead scientist on the Zoe Covid study and professor of genetic epidemiology at King’s College, London, told i he finds it “very odd” that Government campaigns do not list other signs.
He cited sneezing, headaches and a runny nose as possible indicators of the strain, and said that many people do not experience the three symptoms listed by the NHS when they have Omicron.
This came after the Government’s scientific advisers suggested that people contracting the strain were less likely to lose their sense of taste and smell than with previous variants.
Members of the Scientific Advisory Group for Emergencies (Sage) said: “There is some preliminary evidence emerging of changes in reported symptoms with Omicron infection. In particular, loss of taste or smell seem to be reported less frequently.”
Prof Spector added that even if people do display a high temperature, continuous cough or loss of sense of smell, by this point they may have unknowingly infected others and spread the illness.
He told i: “I don’t understand why the NHS posters never mention the cold-like symptoms which are the main sign of the Omicron variant. It is very odd when we are supposed to be trying to curb the spread of this virus.
“As a result, people who are experiencing cold-like symptoms are dismissing them and waiting for signs such as a fever, loss of smell and a cough which are the ones highlighted in all the messaging before thinking they may have Covid.
“The problem is, they either never get these symptoms at all, or if they do, it is after three or four days and they have already infected others by mixing with them.”
According to new analysis from the Zoe Covid app, Prof Spector said an estimated half of all people experiencing cold-like symptoms were likely to have symptomatic Covid and not just a harmless cold.
A Department of Health and Social Care spokesperson said that the Government “acknowledged Covid-19 has a much longer list of symptoms than the ones used in the case definition and experts keep the list of symptoms under review.”
The department said the main Covid symptoms had been carefully selected to capture those most likely to have the virus, while not capturing a great number of people who do not.
How severe are Omicron symptoms compared to other Covid variants?
UK studies into Omicron have suggested that previous Covid infection provides poor protection against the new strain.
Researchers at Imperial College London found that it largely evades immunity from both past infection or having two doses of the Covid vaccine.
However, three UK studies into Omicron published in the week before Christmas indicated that the variant is less likely to cause severe disease than previous Covid strains.
The findings by separate research teams suggested that a lower share of people infected with the new variant are likely to require hospital treatment compared with Delta cases.
Research published by the UK Health Security Agency (UKHSA) suggested that someone infected with Omicron is between 31 per cent and 45 per cent less likely to attend A&E and 50 per cent to 70 per cent less likely to be admitted to hospital than an individual infected with the Delta variant.
Meanwhile, researchers led by Professor Neil Ferguson at Imperial College London calculated a “moderate reduction” in risk from Omicron compared to the Delta variant.
They found that patients infected with Omicron were between 15 and 20 per cent less likely to need to be admitted to A&E than Delta patients and 40 to 45 per cent less likely to be admitted to hospital for one night or more.
A separate, preliminary analysis of Omicron cases in Scotland pointed to an even greater reduction in the risk of hospitalisation compared with Delta.
Scientists on the Eave II study, which is yet to be peer-reviewed, found that people who tested positive for Omicron were around 64 per cent less likely to be admitted to hospital than those with the Delta variant.