Common Cold vs Flu: Understanding the Difference

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People often use the terms cold and flu interchangeably, but they are actually two very different illnesses. Common colds and influenza (flu) are both respiratory illnesses that are caused by different viruses. In their early stages, colds and flu can have similar symptoms. This makes it difficult to know whether you have a cold or the flu. Influenza tends to produce more severe symptoms than the common cold. Read on to find out more about the common cold and flu, how to avoid catching them, and how to treat both of these illnesses.

What Is Influenza?

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Influenza (flu) is a highly contagious respiratory condition caused by the influenza virus. There are many different strains of the influenza virus, and new strains emerge each year. In Australia, flu can be prevented by receiving annual influenza vaccines, which are updated regularly to be as effective as possible. 

Flu is common in Australia. You can catch influenza at any time, but it is more likely during the colder winter months of the year (April to October). Flu tends to peak around August, but 2022 has reported greater numbers of flu than in previous years. With more flu circulating in Australia than normal, it’s even more important to stay aware of the signs and symptoms and what to do if you or a loved one contracts influenza.

Flu can be serious and causes many hospitalisations and GP visits every year. Flu can produce severe symptoms for anyone but is especially risky for older people and infants. Flu is a serious health risk because it can lead to further complications including:

• Bronchitis
• Croup
• Ear infections
• Pneumonia
• Damage to your heart and other organs
• Brain tissue inflammation
• Brain tissue damage
• In severe cases, death.

What Causes the Flu?

Influenza is an infectious respiratory disease caused by the influenza virus. Influenza has three different types – type A, type B and type C. Almost all major outbreaks and severe illnesses are caused by type A or type B. Type C influenza can cause a less severe illness among children which is similar to the common cold. Even though new strains of influenza can emerge each year, they all fit into one of these three main types of flu.

Flu is spread through droplets of bodily fluid that contain active influenza virus cells. If you have the flu, you can expel tiny infected droplets into the air when you cough, sneeze or exhale. These droplets can spread within a one-metre radius and remain suspended in the air. If someone else breathes in these droplets, they can become infected by the virus they contain. 

Flu can also be spread through surfaces. Droplets can land on surfaces and be picked up by another person. If a person with flu blows their nose or covers a cough with their hand, influenza virus particles will be on their skin. Touching people or objects after doing so can transfer the virus to the surface or individual. If that person then touches their mouth or nose before washing their hands, they can become infected with flu.

Signs and Symptoms of the Flu

The symptoms of flu can be very similar to that of the common cold, especially in milder cases or during the early onset of flu. However, there are some specific signs and symptoms to watch for that may indicate you have influenza. These often include:

• Fever (body temperature of 38°C or higher)
• Dry, chesty cough
• Fatigue
• Headaches
• Chills
• Muscle aches
• Pain in your limbs and/or joints
• Nausea or upset stomach
• Diarrhoea
• Runny or blocked nose
• Sore throat
• Loss of appetite
• Sneezing.

Recovering from Flu: How Is Influenza Treated?

Most people are able to recover from the flu on their own, without the assistance of a medical professional. Healthy adults typically recover from the flu within 7 – 10 days without requiring medical treatment. Some people may relieve their symptoms such as pain and fever using paracetamol. 

If you have the flu, you should stay home and rest until you recover to prevent getting sicker or spreading it to others. Some strategies you can use while recovering from the flu are:

• Get plenty of rest
• Stay warm
• Eat plenty of fruits and vegetables
• Avoid any exposure to cigarette smoke
• Drink plenty of non-alcoholic fluids to avoid dehydration
• Inhale steam from a hot bath or shower to relieve congestion
• Gargling warm salt water if you have a sore throat
• Sucking on ice cubes, lozenges or icy poles
• Drinking hot water with honey and lemon juice.

If you are otherwise healthy, most adults don’t need to seek urgent medical treatment if they have flu-like symptoms. However, some people are at a greater risk of becoming seriously ill if they catch the flu. These individuals should see their doctor as soon as possible if they experience flu-like symptoms.

• Children under the age of 5
• Older adults aged 65 and over who live in a residential aged care facility
• People with type 2 diabetes
• People with heart or kidney disease
• Pregnant people
• Individuals with a Body Mass Index (BMI) of 35 or higher
• People of Aboriginal or Torres Strait Islander origin
• People with lung conditions such as severe asthma or cystic fibrosis
• People with diseases that impact muscles and/or nerves, such as muscular dystrophy
• People with weakened immune systems, such as people taking immunosuppressant medications or individual with HIV
• Unhoused people
• People with Down syndrome
• People with liver disease
• People with blood diseases
• People with metabolic disorders
• Smokers

Preventing Flu

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Prevention is the best cure. The best strategies available to prevent influenza infections are vaccination and good hand hygiene. In Australia, it is recommended that everyone over the age of 6 months receives an annual flu vaccine. The strain of influenza virus that causes illnesses changes regularly, and vaccination only protects you for a short period of time, so it’s important to get vaccinated every year. You can find out more about flu vaccines via the Australian Government’s Department of Health.

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Flu is spread by contaminated droplets spread through the air or surfaces. Practising good hand hygiene is important for preventing flu, especially in public places or areas where flu-infected people have spent time. Traces of influenza virus can easily end up on common surfaces like door handles, food, remote controls, smartphones, handrails and computer keyboards. Regularly disinfecting communal surfaces and washing your hands regularly can help you protect yourself and your family from the flu.

What Is the Common Cold?

The common cold is a viral infection that affects your nose, throat and upper respiratory tract (airways). Adults in Australia can expect to have between 2 and 4 colds per year, whilst children can have between 5 and 10. Colds are the most common cause of illness for both children and adults in Australia. There are over 200 virus strains that can produce cold symptoms, which is why there is no vaccine to prevent colds such as those available for influenza.

What Causes Colds?

Most colds are caused by a virus, with the majority a result of one of two main types. The most common virus types that cause common colds are:

• Rhinoviruses
• Coronaviruses.

It is important to note that coronaviruses have been around for a long time. They have caused various illnesses like the common cold, as well as more serious diseases like SARS and COVID-19. Even if caused by a certain coronavirus, not all common colds are as serious as COVID-19.

You can catch a cold at any time of the year, but as with the flu, colds are more common in the colder winter months. Cold weather itself does not cause colds or flu. The reason colds are more common in winter is because people typically spend more time indoors and in close proximity to others. Colds are spread by close contact and breathing in droplets from an infected person’s coughing or sneezing. 

Several viruses cause colds, so it is possible to have multiple colds consecutively, caused by different virus strains.

Signs and Symptoms of Common Colds

Symptoms of a cold can vary between different people. Some people will have few symptoms of relative mild severity. Others will be unwell for longer and have more severe symptoms. Most people will recover from a common cold within a few days to just over a week without medical treatment. Common signs and symptoms of the common cold include:

• Blocked or runny nose
• Sore throat
• Cough
• Sneezing
• Red or swollen eyes
• Headaches
• Swollen lymph glands
• Loss of appetite.

Less common cold symptoms include fever and vomiting or diarrhoea. Fever can be a sign that your illness may actually be the flu and not a common cold.

For most healthy adults, the common cold does not become severe. Most people recover from the common cold without medical treatment. However, you should consult your doctor if you have cold or flu symptoms if one or more of the following apply to you.

• You can’t drink fluids or keep them down
• You experience frequent vomiting
• Your headaches become intense
• You feel sleepy and become pale
• You experience chest pain
• Your cold symptoms last more than 10 days
• You have a fever and a rash
• You have trouble breathing
• You are worried about your health
• You have a pre-existing chronic health condition

If you have a young child with cold symptoms, and they are not feeding, have trouble breathing, is dehydrated or showing signs of severe illness, seek medical advice.

If you have a cold, you should stay home to recover and avoid spreading it to others. Do not take antibiotic medications if you have a cold. Colds are caused by viruses, so antibiotics will not help you as they are designed to treat bacteria. Taking antibiotics when you don’t need them can have side effects such as an upset stomach. You can take over-the-counter medications like paracetamol to alleviate pain or fever.

The Difference Between the Common Cold and the Flu

Determining whether you have a cold or the flu can be tricky. This is because the two illnesses share many signs and symptoms in common. Knowing whether you have a cold or the flu can be important if you are at risk of becoming very unwell with influenza. 

Flu and cold symptoms can be very similar, but flu symptoms are typically more severe and last for a longer period. The two best signs to look for to determine if it is a cold or the flu are your temperature and how your limbs and joints feel. 

Fever and body aches and chills can be more likely with flu, whereas congestion, sore throat and cough without a fever or body aches can indicate it is a common cold. Sneezing and a runny nose may be more common when you have a cold and less likely if you have the flu. 

If you have a cold, you will likely have mild to moderate fatigue and malaise. It will likely only last a few days. However, if you have the flu you may experience more severe exhaustion that lasts several days.

In children, diarrhoea and vomiting can be a symptom of flu. Diarrhoea is usually not associated with colds in children or adults, so if you have a child with cold symptoms and vomiting and/or diarrhoea, they may have the flu.

The Australian Government has provided a useful infographic outlining common signs and symptoms of both cold and flu. The infographic can be a useful way to check your symptoms and get an idea of the underlying illness causing them. This information is general advice only, if unsure you should always seek personalised medical advice through your family doctor.

Preventing Common Colds and Flu

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Regardless of whether it is the flu or a common cold, nobody wants to become unwell or risk spreading illness to their loved ones. Prevention is the best way to protect you and your family from catching a cold or the flu and becoming seriously unwell. The best way to prevent infectious diseases like colds and flu is to practise good hand hygiene, especially in public places. Avoid close contact with people displaying cold or flu-like symptoms, and if you are unwell, stay at home to prevent infecting others. Getting your annual flu shot is the best way of protecting yourself against influenza. Flu shots are especially important for people at higher risk of becoming very unwell with the flu, and those who work in close proximity to vulnerable people, such as aged care and health care workers.