The Omicron variant of Covid-19 has been around for almost a year, with the variant now having sub-lineages including BA.4 and BA.5.
But what are the signs and symptoms of Omicron and how have they changed since the strain first emerged?
We spoke to Martin Michaelis, professor of molecular medicine at the University of Kent, to understand more.
What are the symptoms of Omicron?
Some of those vaccinated against Covid have recently shared a common symptom. After testing positive for the virus, around one in five vaccinated people in the UK with Omicron or Delta strain experiencing diarrhoea as a symptom.
Although common symptoms of Covid include fatigue, a sore throat, and headaches, according to data gathered by the ZOE Health Study app, diarrhoea is a common symptom of Covid for vaccinated people in the UK.
Data showed that there was a rise in people reporting this symptom in January 2022, and that some of this was related to the Omicron variant of Covid-19.
The team added that diarrhoea can be an early symptom of Covid, starting on the first day of infection and getting worse throughout the week.
The ZOE team said: “It usually lasts for an average of two to three days, but can last up to seven days in adults.”
They found that this symptom has become less prevalent with each variant, as nearly a third of adults aged over 35 reported having diarrhoea during the Alpha wave, but just one in five said they experienced it during the Omicron and Delta waves.
The people who experienced it during the latter two waves had been vaccinated either twice or had also received their Covid booster jab.
If you have diarrhoea along with other common Covid symptoms, like a high temperature, a new cough, and a loss or change of your sense of taste or smell, then you may have Covid.
What are the other common symptoms of Covid?
Symptoms of Covid in adults can include:
- A high temperature or shivering (chills) – a high temperature means you feel hot to touch on your chest or back (you do not need to measure your temperature)
- A new, continuous cough – this means coughing a lot for more than an hour, or 3 or more coughing episodes in 24 hours
- A loss or change to your sense of smell or taste
- Shortness of breath
- Feeling tired or exhausted
- An aching body
- A headache
- A sore throat
- A blocked or runny nose
- Loss of appetite
- Feeling sick or being sick
What causes symptoms to change?
Martin Michaelis, professor of molecular medicine at the University of Kent, said many of the symptoms associated with an infectious disease are actually caused by our immune system fighting a pathogen, including symptoms such as fever, chills, headache, sore throat, coughing, runny nose, fatigue, body aches, hoarse voice, diarrhoea, nausea, and vomiting.
He said that “it is not surprising” that disease symptoms change when an infectious disease like Covid-19 circulates for a prolonged time.
This is due to two factors. The first is that vaccinations and previous infections change the way in which our immune system responds to coronavirus, with immune responses becoming more effective and specific, and this also changes the symptoms that we experience.
The second factor is that enhanced immunity within the population means that “the virus itself has to change to still be able to infect people,” Prof Michaelis added, so new virus variants “evolve through random mutations”.
These new versions differ in their properties from previous ones and can cause different symptoms.
There is therefore “an ongoing fight between our immune systems and the virus, which means that both the virus and our immune response continuously change and adapt to each other,” added Prof Michaelis.
These changes are then reflected in the changes in symptoms that people experience over time.
Prof Michaelis noted that those with Covid may suffer from all infectious disease symptoms described above, but the relative frequency of these symptoms differs between the different variants.
Originally, a consistent cough and a loss of taste and smell were the most characteristic Covid symptoms, but the emergence of the Omicron variant at the end of 2021 resulted in a shift towards more generic common cold symptoms like a sore throat, headache, and a runny nose.
Dizziness and fainting were then more frequently described in Covid patients when Omicron became the dominant virus variant.
How symptoms differ in Omicron sub variants
The currently circulating Omicron variant is also not the original version anymore, with Omicron having evolved into different sub variants.
Originally, the sub variants BA.1 and BA.2 were responsible for most of the Omicron cases, with the most recent surge of Covid infections then being caused by the sub variants BA.4 and BA.5, with BA.5 being the dominant sub variant.
According to recent findings, BA.5 seems more often to cause a blocked nose and a dry cough than previous variants, but a sore throat and headache remain the symptoms that are most commonly reported by BA.5 patients, Prof Michaelis said.
He said: “There is a continuous shift in the symptoms experienced by Covid-19 patients. However, it is important to keep in mind that the Covid symptoms are individual to each infected person and can substantially change in the same individual each time they are infected.
“If you are infected by Covid-19, your symptoms may completely differ from those reported by the majority. Hence, it is impossible to know whether you have Covid-19 purely based on your symptoms. Only a test will tell you whether you have Covid-19 or not.”