COVID-19 and the flu can cause similar symptoms. However, there are several differences you should be aware of.
Medically reviewed by Dr Louise Wiseman MBBS, BSc (Hons), DRCOG, MRCGP and words by Zia Sherrell
Sneezing, coughing, runny nose? The COVID-19 pandemic means most people are paying close attention to every sniffle and splutter.
Before coronavirus, we were likely to put down minor respiratory symptoms to a common cold, influenza, or allergies. For peace of mind, you should understand the difference between COVID-19 and other conditions that could appear similar, at least initially.
The difference between COVID-19, the flu and a cold
Different viruses cause all three of these conditions, which is why there is some cross-over in the symptoms. If you can easily mistake COVID for the flu or a cold, how can you tell the difference?
‘COVID-19, flu, the common cold, and allergies have a lot of overlapping features. There are a few characteristics, however, that may lead one to suspect COVID-19 over the others.’ Dr. Adam Wellikoff, Pulmonologist at the Pulmonary, Critical Care, and Sleep Disorders Institute of South Florida told NetDoctor.
He continues that ‘the triad of fever with a dry cough and shortness of breath should raise suspicions. Particular attention should be paid if a person has had recent travel or contact with a COVID-19 positive person.’
Some symptoms that you may be concerned about are not indications of COVID-19. Dr Wellikoff tells us that ‘other features such as runny nose [and] productive cough make something other than COVID-19 more likely.’
‘There are a few characteristics that may lead one to suspect COVID-19 over the others’
If you have respiratory symptoms and a fever, or any other mild symptoms, the only way to categorically tell if it’s a COVID-19 infection is to take a test. However, that’s not an option for many people so, instead, you should look out for the tell-tale signs of a fever combined with shortness of breath. Many patients display this common sign of COVID-19 before their health deteriorates, and they develop pneumonia.
The common cold rarely causes fever and generally is much less severe than the flu or COVID-19. People with colds usually have a runny or stuffy nose which is rare in coronavirus infections. Colds rarely cause serious health problems, such as pneumonia, secondary bacterial infections, or hospital admissions. Flu can have serious associated health complications.
From what we know so far, the typical symptoms of COVID-19 are:
- A high temperature
- A new, continuous cough: coughing for more than an hour, three three or more coughing episodes in 24 hours, or if your usual cough is simply worse than normal.
- Shortness of breath
Other symptoms reported include:
- Body aches
For most people, fever is the first symptom, followed by the dry cough, with shortness of breath developing in some people around 5-10 days following the initial symptoms.
Countless studies report that fever, shortness of breath and a dry cough are the primary symptoms that affect most COVID-19 patients. A study of 138 COVID-19 patients in China showed that 98.6% of the patients had a fever, and 59.4% had a dry or nonproductive cough. Around a third of the patients had difficulty breathing or dyspnea to use the medical term.
‘For most people, fever is the first symptom’
A fever is usually a raised temperature of at least 37.8°C in an adult but can simple be measured by being hot to touch on the chest or back. For most people, fever is the first symptom, followed by the dry cough, with shortness of breath developing around 5-10 days following the initial symptoms.
Shortness of breath means that you unexpectedly feel out of breath. If you’ve just done your daily workout, or run up and down the stairs, you would expect to feel a little short of breath. Some people feel breathless when they are anxious, but when they are calmer, their breathing returns to normal. These are examples of occasions when you shouldn’t worry if you have a little shortness of breath.
If you find that you need to breath harder under normal circumstances, you should talk to your doctor. Remember that if it’s your only symptom, the cause is probably not COVID-19.
When to see a doctor
Dr Ramprasad Gopalan, Infectious Disease Physician, and owner of First-Class Medicine tells us that the clinical course of COVID-19 is predictable. He said that ‘2-11 days after exposure (day 5 on average) flu-like symptoms start.’
He continues ‘the time to seek emergency medical attention is new onset of shortness of breath or when symptoms become unmanageable at home.’
If you think you may have a cold, flu or COVID-19, and you are having trouble breathing, you should contact your healthcare provider. Try not to panic because influenza and COVID-19 can cause almost identical symptoms.
Severity of symptoms
An interesting feature of COVID-19 is its broad spectrum of symptoms and variation in severity. Some people are entirely asymptomatic, which means they show no symptoms, feel completely well, and usually have no idea that they are infected.
‘Some people feel completely well and have no idea that they are infected’
Asymptomatic carriers can still spread the virus to others, even if they have no respiratory or other symptoms, although not as effectively as people with active infections.
You may be wondering how many infected people are asymptomatic, and the answer is that it’s difficult to say. Most countries are only testing sick people, which of course misses asymptomatic carriers. The Government of Iceland tested a large proportion of their population and found that half of those who tested positive showed no symptoms.
One confusing symptom that you find in common with allergies, colds, flu and COVID-19 is a cough. All coughs are not created equal, and this is the decisive point.
You need to consider the differences between types of cough.
Additional symptoms such as a runny nose, or irritated eyes accompany coughs associated with seasonal allergies.
Coughs that accompany colds, flu and COVID-19 could be more challenging to tell apart.
‘All coughs are not created equal, and this is the decisive point’
A dry, persistent cough can be an early sign of all three conditions. Coughs that indicate a cold are usually productive or could be tickly and irritating. COVID coughs are typically dry and hacking and cause some level of chest pain.
The NHS states that ‘a new continuous cough – this means coughing a lot for more than an hour, or 3 or more coughing episodes in 24 hours’ can be a symptom of COVID-19.’
Many patients report that a COVID-19 cough is dry and hacking. It can cause moderate chest pain because of inflamed bronchial tubes.
Influenza can also cause a cough. There could be wheezing, and your chest might feel tight. In the early stages, a productive cough is rare. In the later stages, you might cough up phlegm.
Loss of smell could be a COVID-19 symptom
Have you ever had a cold and not been able to taste or smell anything? Viral infections can cause of loss of sense of smell.
Experts are finding increasing evidence that shows SARS-CoV-2 can cause anosmia or loss of smell. In the report from Germany, two of the three COVID-19 patients reported a loss of sense of smell. A large proportion of people with mild symptoms in South Korea reported anosmia as their primary symptom.
‘Experts are finding increasing evidence that shows SARS-CoV-2 can cause anosmia or loss of smell.’
Anosmia could help doctors identify asymptomatic COVID-19 carriers. Further studies are needed to find out how common this symptom is and at what point after infection people lose their sense of smell.
Remember that other allergies and viruses can cause loss of smell caused by allergies, but if you suddenly can’t smell your dinner cooking, you might want to look out for other symptoms and potentially discuss with a health professional.
Sneezing is not a COVID-19 symptom
The common cold is a viral infection that frequently causes sneezing, and upper respiratory symptoms like a runny or blocked nose, and sinus or facial pain. You may also experience these symptoms with the flu or allergies. However, COVID-19 does not typically cause these symptoms.
In a study of clinical characteristics of 140 COVID-19 patients in Wuhan, China, sneezing was not reported as a symptom in any patient.
In a World Health Organisation report that looked at nearly 60,000 COVID-19 patients, congestion was reported in just 4.8% of cases.
Allergies can have chronic symptoms
Many people experience seasonal allergies or allergies to pets that can cause symptoms that might concern them in light of the COVID-19 pandemic.
Sufferers of allergic rhinitis, or to use its common name, hay fever, can experience the following symptoms:
- itchy, watery, red eyes
- Itchy skin or a skin rash
- blocked or runny nose with thin, clear mucous
- wheezing in some cases
These are not symptoms of coronavirus.
The primary way to distinguish between a COVID-19 infection and allergies is the presence of a fever and shortness of breath. Allergies don’t cause a fever.
Dr Dilraj Kalsi, the founder of Hippocrates Lounge, explained ‘colds and allergies do not involve fever, but allergies involve itchy eyes.’
People with allergies usually don’t have shortness of breath. The exception is in those who have asthma that flares up when they are in contact with allergens.
If you have sore muscles, body aches and fatigue, it won’t be due to allergies. These symptoms are associated with more severe viral infections like COVID-19 and the flu.
Do you have COVID-19 symptoms?
It’s important to try and keep perspective with any symptoms you may have. Cold, flu and allergies are still common findings. Follow expert recommendations and if you are concerned you have the coronavirus, use the NHS 111 coronavirus service which will direct you to the appropriate healthcare.