Do you have a sore throat, runny nose, body ache or fever? It could be a common cold, the flu or Covid-19 as the symptoms are very similar.
People suffering from these symptoms may wonder if they have Covid-19 and should isolate and take a test.
But they may also be tempted to think it is just a cold.
With the Northern Hemisphere in the middle of its winter, when influenza cases tend to peak (the season runs from early October to mid-May), flu may be suspected too.
Given that the Omicron coronavirus variant may be more likely to lead to mild symptoms, people may feel it is harder than ever to distinguish between the various respiratory infections going around.
Here we take a look at the issue and ask experts for advice.
Does Omicron cause the same symptoms as the common cold?
Based on symptoms alone, it may be difficult to tell apart the common cold and Covid-19, especially when it is caused by the Omicron variant.
This shows the importance of testing.
“A common cold and Omicron is, in my view, impossible to distinguish,” Prof Eskild Petersen of Aarhus University Hospital in Denmark, who chairs the European Society of Clinical Microbiology and Infectious Diseases, told The National.
It is a point echoed by Dr Andrew Freedman, an infectious diseases specialist at Cardiff University in the UK.
“A lot of people, particularly vaccinated people, are getting what would otherwise be thought of as the common cold,” he said.
The UK’s National Health Service said that the main symptoms of Covid-19 include a high body temperature, a new, continuous cough and loss or change to the sense of taste or smell.
Some of these overlap with common cold symptoms, which may also include a blocked or runny nose, muscle aches and sneezing.
Will Sars-CoV-2 become another coronavirus that causes the common cold?
Some researchers have forecast that Sars-CoV-2, the coronavirus that causes Covid-19, will eventually largely cause only cold symptoms.
Four other coronaviruses that infect people do in fact cause the common cold. One of these four is called HCoV-OC43.
Researchers have proposed that OC43 may have been responsible for the “Russian flu” pandemic that began in 1889 and went on to kill about one million people.
While OC43 can still cause severe illness in certain groups, such as infants, the elderly and people with a weakened immune system, it usually causes simply a cold.
This may be because we are infected with it periodically, so have a background level of immunity.
Sars-CoV-2 may be moving in the same direction, given that the Omicron variant, while highly transmissible, appears to often cause milder symptoms.
There is also now wider immunity to the virus thanks to vaccination and previous infection.
Can influenza and Covid-19 be told apart?
While distinguishing between the common cold and a mild case of Covid-19 is difficult based on symptoms alone, infectious diseases experts said flu is more likely to produce different indicators.
“Flu can be a more severe illness with aches and pains,” said Dr Freedman.
In particular, influenza may cause a person to develop muscle pain and back pain, said Prof Petersen, symptoms that are not typically associated with Covid-19, especially when it is caused by the Omicron variant.
“If you really have influenza, you have fever and general muscle pain,” he said, adding that a loss of smell – sometimes seen with Covid-19 – is typically not found with flu.
As well as an aching body, the NHS said that flu symptoms, which may arise rapidly, can include a sudden increase in body temperature (38°C and above), feeling tired or exhausted, a dry cough, a sore throat and a headache, among others.
What should people do if they have symptoms that could be Covid-19?
Rules vary from country to country, but as a general piece of advice, experts say people with possible Covid-19 symptoms should self-isolate and get tested, ideally with a PCR test as these are more accurate.
A key point emphasised by health organisations such as the US Centres for Disease Control and Prevention (CDC) is that people infected with the coronavirus can pass the pathogen on even when they have mild or no symptoms.
“CDC expects that anyone with Omicron infection can spread the virus to others, even if they are vaccinated or don’t have symptoms,” the organisation said in an online briefing last month.
Vaccination remains widely recommended as a way of reducing the chance of admission to hospital, severe illness and death, although people with Covid-19 symptoms should not be vaccinated until they recover, the NHS advises.
It said people should wait 28 days after a positive test or after symptoms started before getting inoculated.