The Ultimate Guide To Cold & Flu

Protect yourself and others from cold and flu viruses this winter with our definitive guide on everything you need to know about the two common viral infections.

Published: Thursday 22 December 2022

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Although it’s possible to catch a cold or the flu all year round, the autumn and winter months are widely regarded as ‘cold and flu season’. Whilst most of the usual symptoms can cause discomfort, they are usually not serious and do not require medical attention.

There are plenty of ways to prepare for the cold and flu season to reduce your chances of getting yourself or others sick. Find out everything you need to know about the common cold and influenza in this ultimate guide, covering the differences between the two respiratory infections, symptoms, available treatments and prevention measures!

Common Cold

What is a cold?

The ‘common cold’ is a viral infection of the upper respiratory tract (the throat and nose) which can be caused by up to 200 different species of viruses. The symptoms, although unpleasant, are usually harmless. It is thought that the average adult will catch 2 - 4 colds each year, whereas children may experience 6 - 10 colds every year due to their underdeveloped immune systems^[1].

What causes a cold?

The common cold can be caused by several different types of viruses, with the rhinovirus being most commonly experienced, which accounts for 10-40% of colds^[2]. Other viruses that can commonly cause a cold include coronaviruses or the respiratory syncytial virus (RSV)^[3].

What are the symptoms of a cold?

Symptoms of a cold can appear gradually, mainly affecting the membrane linings of the nose and throat. They typically include^[4]:

• Congestion of the sinuses
• A runny nose
• A sore throat
• Sneezing
• A mild cough
• Post-nasal drip

Less common symptoms of a cold can include:

• Fatigue
• Muscle aches
• A temperature of 38°C or higher
• Pressure in the ears and face
• A loss of taste or smell

How long do cold symptoms last?

Most people recover from a cold within a week, although symptoms can occasionally last up to 10 days. For children, the elderly or those who are immunocompromised, symptoms may last longer.

Stages of the common cold

Once infected with a cold, it will go through several cyclical stages that determine which symptoms you experience and how likely you are to spread the cold to someone else. These stages are:

• Incubation Period:

The incubation period is the duration between when you first become infected with a cold and when you first begin to display symptoms. Most cold viruses, such as the rhinovirus, have short incubation periods, but ultimately the duration of the incubation period depends on the virus that has caused the cold. For example, the rhinovirus has an incubation period of 2-7 days whereas RSV has an incubation period of 4-5 days^[5].

• Stage 1 (Day 1-3):

After the incubation period, the first set of symptoms you are likely to experience may include an irritated throat, a runny nose, sneezing and feeling more tired than usual. The arrival of these symptoms mean you are now contagious and can spread the virus to others.

• Stage 2 (Day 4-7):

At this point, you may be experiencing the worst of the cold’s symptoms. It is likely that your sinuses will feel blocked and inflamed, your throat will be sore and you may be coughing frequently. Similarly to stage 1, you are still contagious at this point.

• Stage 3 (Day 8-10):

At this point, you will most likely still experience symptoms, such as a cough, runny nose and fatigue, however they will be less severe than during stage 2 and will begin to subside. So long as your symptoms are present, irrespective of their severity, you will still be contagious so it’s important to prevent spreading the virus to others.

Influenza

What is the flu?

The flu is regarded as a contagious respiratory infection (affecting the throat, nose and sometimes lungs) caused by influenza viruses. Although the flu can be caught all year round, it is most commonly spread during winter months.

What causes the flu?

The flu is specifically caused by the 3 different strains of the influenza virus that affect humans: A, B and C. Influenza A and B viruses are the most common, and typically cause the larger, seasonal outbreaks that we see during winter months.

What are the symptoms of the flu?

Unlike a cold, symptoms of the flu appear very fast and affect the other areas of the body (e.g. the head, muscles and digestive system), as well as the respiratory tract. They are also generally more severe than the symptoms of a cold, and may include^[6]:

• Sore throat
• A dry, chesty cough
• Headaches
• Body aches and pains
• Fatigue
• A sudden fever of 38°C or higher
• Trouble sleeping
• Nausea and vomiting
• Diarrhoea or stomach pains

Less common symptoms of the flu include:

• Sneezing
• A runny nose
• Congestion

How long do flu symptoms last?

For most people, although symptoms of the flu are uncomfortable, they should only last for 1 - 2 weeks. After symptoms have cleared, you may still experience fatigue. Similarly to the cold, children, the elderly or those who are immunocompromised may take longer to recover.

Stages of the flu

Like the cold, the flu develops through several stages before you recover, with each stage affecting the symptoms you are likely to experience. These stages are:

• Incubation Period:

The incubation period for the flu can vary from person to person, but on average has a duration of 2 days^[7]. The incubation period is fairly consistent across different strains of the influenza virus.

• Stage 1 (Day 0):

After contracting the flu, even though you are not experiencing any symptoms at this point, you are now contagious and can spread the virus to others. It is likely that you came into contact with someone infected with the flu within the last 48 hours. The influenza virus starts its infection of your body by hijacking your cells and making duplicates of itself to increase its spread.

• Stage 2 (Day 1-4):

On day 1 of your infection, it is likely that you will wake up feeling normal. However, the onset of flu symptoms can be sudden, meaning that by the end of day 1, you may be feeling several symptoms at once. Your symptoms will probably include a sudden high temperature, headaches and fatigue. Over the next few days, you may experience the peak of the flu symptoms, which could include body aches, a dry cough and sore throat. You are still highly infectious at this point.

• Stage 3 (Day 5-7):

At this point, flu symptoms generally begin to subside. Your high temperature may have gone, and the severity of your other symptoms will decrease. You may feel like you have more energy. It is likely that you are becoming less contagious at this point, however you should still take precautions to avoid spreading the virus to others.

• Stage 4 (Day 8+):

By day 8, you may still feel tired but the majority of your symptoms should be gone. If you have not already, you should be okay to return to work or school, and continue with your normal routine. If at this point you are still experiencing severe symptoms, you should seek medical attention, as this could mean you have developed a secondary infection such as pneumonia or bronchitis.

What is the difference between a cold and the flu?

It can sometimes be difficult to tell the difference between a cold and the flu based on symptoms alone. They are both common, contagious viruses that mainly affect the respiratory tract, and peak during the winter season.

When it comes to telling the two respiratory viral infections apart, there are several key differences. Firstly, a cold can be caused by up to 200 different viruses, including the rhinovirus, parainfluenza viruses and coronaviruses. The flu, however, is caused strictly by influenza viruses. Secondly, whilst there is some overlap in the symptoms of both infections, flu symptoms are usually more severe, appear more quickly and take slightly longer to clear. In addition to this, flu symptoms affect more than just the respiratory tract, including the digestive system, muscles and joints, and the head. While most people recover from both illnesses without requiring any medical attention, the flu carries a higher risk of developing into a secondary infection, like pneumonia, bronchitis or another bacterial infection. That said, this is rare and is more likely to occur to someone who is immunocompromised, has an underdeveloped immune system or a long-term medical condition.

Can a cold turn into the flu?

Although there is an overlap between symptoms, a cold cannot develop into the flu. This is because the flu is caused by influenza viruses, whilst the common cold is caused by up to 200 different viruses.

Can you get a cold and the flu at the same time?

Due to the high number of viruses that could possibly cause a cold, and the multiple forms of flu virus, it is possible to be infected with the flu and a cold at the same time. However, not only is this rare, but it is unlikely that you would notice a cold if you were already experiencing the flu. With that in mind, if this does occur, you may experience a longer duration of symptoms, or increased severity in symptoms, as your immune system is defending your body against more than one viral infection.

Why are colds and flu more common in winter?

It’s often thought that the cold weather alone can make us ill, however this is not true. That said, there are several reasons as to why you are more likely to experience a cold or the flu during winter seasons, including^[8]:

• More time spent indoors: When it’s cold, we spend more time inside, in closer proximity to other people with prolonged face-to-face contact. This increases the likelihood of catching a viral infection from someone else.
• Lower humidity: During winter months when the temperature drops, the air becomes drier due to drop in humidity. This has several knock-on effects that increase our likelihood of becoming infected. Firstly, when an infected person sneezes or coughs, the particles the droplets they release that carry the virus dry up quickly, leaving the virus particles to stay airborne indefinitely. Secondly, lower humidity can cause irritation to our nasal passages and airways, making us more susceptible to developing an infection.
• Colder temperatures: During the summer, the hotter weather can denature the proteins that make the virus’ protective capsule, meaning they lose their functional shape and die. However, when it’s colder, this hardens the viruses’ structure, making them more adaptable to survive the lower temperatures.

How can I treat cold or flu symptoms at home?

Often, colds and the flu will clear on their own without the need for medical attention. However, as the symptoms are often unpleasant, make you feel run-down and can be contagious, it is recommended you:

• Get plenty of rest and sleep
• Keep warm
• Drink a lot of fluids to prevent dehydration
• Stay home from work or school (this may only be necessary if you have a high temperature or do not feel well enough to carry on with your normal routine)
• Gargle salt water to soothe a sore throat

What cold and flu medicine can I take?

There are a variety of treatments you can take to relieve and ease cold and flu symptoms:

• Paracetamol: This is a popular pain-relief medication which can ease cold and flu symptoms such as body aches, headaches and sore throats. As well as this, paracetamol can also lower high temperatures.
• Ibuprofen: This is another common pain-relieving treatment, belonging to the category of medications known as nonsteroidal anti-inflammatory drugs (NSAIDs). This means ibuprofen effectively reduces inflammation and swelling which can occur during a cold or flu. In addition, it also helps lower fevers.
• Tamiflu: This is an antiviral medication which can be used to relieve flu symptoms and prevent the flu spreading. Tamiflu contains the active ingredient oseltamivir, which works against influenza by inhibiting the formation of the enzyme neuraminidase - which is necessary for the flu to spread.
• Vicks Vaporub: This is a topical treatment that works to relieve cold symptoms. Its active ingredients (camphor, eucalyptus oil and menthol) have cough suppressing qualities and are topical analgesics, which provide local pain relief.

Antibiotics for colds and flu

Sometimes it can take a while to relieve cold and flu symptoms, so people often feel that they may need stronger medication, such as antibiotics. However, this is not recommended. Antibiotics cannot treat viruses - antibiotics are antimicrobial medications that fight bacterial infections and prevent them from spreading by inhibiting their growth. As colds and the flu are caused by viruses, antibiotics can’t actually treat them, nor can they speed up your recovery.

How to prevent catching a cold or the flu

To reduce your chances of spreading a cold or the flu to others or catching them yourself, it is recommended that you:

• Regularly clean surfaces that you touch often, such as countertops, door handles and electronic equipment.
• Regularly wash your hands with soap and water.
• Use tissues to cover your nose and mouth when coughing or sneezing, bin these tissues as quickly as possible after and then wash your hands thoroughly.
• Wear a face mask while on public transportation or in public places.
• Get your flu jab annually
• Support your immune system by:
• Eating nutritious diet
• Getting 7-9 hours of sleep, as well as plenty of rest
• Take vitamin and mineral supplements
• Reducing stress levels where possible
• Exercising regularly (150 minutes per week)

If you have a high temperature, you should also stay home and limit contact with other people.

Remember, most cases of cold or flu are not anything to worry about. Although symptoms can be irritating, make you feel run-down and can sometimes impact your normal routine, they usually go without requiring medical attention. Staying hydrated, eating well and getting plenty of rest should help to boost you back to your normal self - just make sure you also take precautions where necessary to prevent spreading a cold or the flu to others or catching it yourself!