Runny nose, cough, lost your sense of taste or smell? GP and Covid survivor Dr Johanna Ward explains the difference between the 3 illnesses and when you should go for a Covid test

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With the return to the office in full swing, coughs and cold are being passed around again (thanks, commute!) but with the threat of Covid still present, everyone wants to know how to tell the difference between a common  cold,  cough, the flu and Covid so that they can self-isolate if necessary. Because the symptoms of flu and Covid especially are similar, and because a cold can often be accompanied by a cough, one of the key Covid-19 symptoms, it can be difficult to tell them apart. But there are some differences between them that may help you decipher whether you're just bunged up with a runny nose or whether you have something more serious.

What Covid 19 feels like

When I got Covid back in March 2020,  I had a fever that came on really quickly over a few minutes and a strange, sharp, deep chest pain that I had never experienced before. Despite being incredibly poorly with Covid (I had pneumonia) I barely had a cough which felt very odd. Instead, I had fever, fatigue, chest pain, difficulty breathing, diarrhoea, headache and loss of taste and smell with a densely blocked nose. I knew it was something more serious than cold or flu because every system in my body felt like it was under attack.

What are the similarities between a cold, cough, flu and Covid?

Covid, colds and influenza are all respiratory illnesses (ie they affect your lungs) and they are contagious and spread through other people’s infected respiratory droplets (their coughs or sneezes) getting into your respiratory system, either by you touching a surface that they have infected (such as shaking their hand) or somehow breathing in their droplets (hence the need to wear a mask to stop a sneeze, for example, travelling as far).

A cough is a symptom of all three of these rather than a condition in itself.

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They are caused by different viruses: Covid 19 is caused by a new virus called SARS-CoV-2 and flu is caused by the influenza virus normally Influenza A or Influenza B. (The flu jab generally inoculates you against a certain strain of flu. Flu viruses are constantly changing so the vaccine is reviewed and adapted each year according to the strains that are around. The jab doesn’t protect you from all the different strains so you can still get it even if you have been vaccinated).

Colds are caused by several different viruses, including a type of coronavirus, parainfluenza virus or rhinovirus. Common colds are generally much less severe than influenza or Covid although in young babies and children they can cause significant respiratory distress.

Both Covid and flu can cause infections that can be mild or full-blown involving the lungs (pneumonia) or many other systems of the body as well as sepsis (infection and inflammation in the blood). They can both sadly be fatal too.

The good news is that these viruses are reduced with social distancing and hand hygiene measures so it’s very important that we continue these measures throughout the winter months. When it comes to Covid and flu, they can literally save lives.

How do I know if it’s Covid? The main symptoms

• Fever/high temperature: anything above 38 degrees C. You feel hot to the touch on chest and back.

• Cough: any kind of new continuous cough. The NHS describes it as coughing a lot for more than an hour or having three coughing episodes in 24 hours, or if you normally have a cough it's worse than usual.

• Shortness of breath: finding it hard to talk in full sentences or feeling breathless on exertion

• Headache:  this can be associated with Covid

• Loss of taste or smell: this been added to the Government's official list of Covid symptoms so if you get loss of smell or taste I suggest that you presume you have Covid until a negative test tells you otherwise. Loss of smell and taste aren’t strongly associated with flu so this is quite a helpful differentiating symptom for Covid.

• Fatigue

• Children can experience the same symptoms as adults with Covid but they also seem to get gastrointestinal symptoms such as nausea, vomiting and diarrhoea so be mindful in children of these kinds of complaints

How long is the Covid incubation period?

This is the point at which you have contracted the virus but don’t know it yet. The average is five days but it can be up to 14 days. This is why when we are being told to self isolate we have to isolate for ten days because it can take that long to develop symptoms. When you are in the incubation period with Covid you might feel perfectly fine but you are highly contagious. This is why Covid is so dangerous.

How quickly does Covid develop?

With Covid, symptoms come on more slowly than they do with influenza so they build over a few days. By day five to seven of Covid most people experience the peak of their symptoms. I certainly felt my worst on day six with significant shortness of breath and chest pain. It was only on day seven that I lost my sense of taste and smell.

What are the symptoms of flu and how do I know it’s not Covid?


• Fever/temperature greater than 38C

• Body and muscle aches

• Fatigue

• Dry cough

• Sore throat

• Nausea

• Body chills

How long is the flu incubation period?

The incubation period for flu appears to be about one to three days but with Covid, it’s longer at about five days and up to 14. Influenza the symptoms come on more quickly and abruptly, typically within a day or two of contact.

How do I know if my symptoms are a common cold?


• Runny nose

• Cough

• Tiredness

• Sore throat. This is common in a cold, less common for Covid.

A fever is uncommon with a cold in adults and most people suffering from a cold. You aren’t incapacitated or bedridden with cold symptoms so it’s generally a much milder disease than flu or Covid. Most people recover from a cold within a week or so whereas flu and Covid can make people unwell for several weeks

Because influenza and Covid have a lot of symptom overlap the best thing to do if you are worried you might have either is to get a diagnostic test. The standard test to diagnose Covid involves swabs being taken from deep inside the mouth and nose. Its a painless procedure and gives results in 24 to 48 hours.

With Covid, data seems to suggest that approximately 80 per cent of infections are mild or asymptomatic, 15 per cent are severe (requiring medical intervention) and five per cent critical (requiring ventilation). The chance of severe or critical illness is higher for Covid than the flu at present but this may change over time as we learn to manage Covid better and if a suitable vaccine is developed.

Dr Johanna Ward studied English Literature at Oxford University before moving to London to start her medical studies at Guys Kings and St Thomas Medical School. She worked in A&E & trauma medicine before becoming a GP with an interest in skin and nutrition. She is the founder of Zenii Vitality and Skincare and author of  Superfoods to Super Health: intelligent and sustainable food choices for the next generation.