Cold, Flu, Bronchitis and Pneumonia – The Difference Explained - DoctorDoctor
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Cold, Flu, Bronchitis and Pneumonia – The Difference Explained

With the colder weather will come a range of winter illnesses – the dreaded flu, cold, bronchitis and pneumonia. Are these all just a difference of degree or are they different conditions? The confusion stems from the similarity of symptoms. Although they are mostly respiratory in nature, they are very different based on whether they are caused a virus or bacteria, the organ they attack and the treatment they receive.

The common cold

Let’s start with the common cold. Called so because it is the most common infectious disease in the world. It is caused by a virus and has 200 known strains. That’s why even if our body develops antibodies to one strain, we could get a cold from another. That’s the reason children get 5-10 colds a year and most adults get only 2-4. And since antibiotics don’t kill viruses, no medication is recommended for the common cold, although OTC drugs could help ease some of the symptoms. Colds are very rarely seriously.


The flu is completely different from the common cold. It is caused by the Influenza A or B virus. It is accompanied by high fever and for vulnerable groups with low immunity a flu can be quite serious and in some cases life-threatening. It is usually accompanied by high temperature. Speak to your GP if you’d like to know more about the flu vaccination. The government offers them free for some high-risk groups. However, the flu virus mutates very quickly and the vaccine does not provide protection against all strains.


Bronchitis is the inflammation of the airways leading to the lungs. Bronchitis often develops from the common cold. It manifests as a frequent cough. When acute, bronchitis can take 10 days to clear, though the cough could hang around for much longer. More vulnerable are those whose respiratory system has been compromised through smoking or environmental pollution. Others with low immunity are also at a greater risk. Chronic suffers need to be under a management plan worked out by their GP, so if you have been coughing very often, it’s a good idea to make an appointment.



Both, the common cold and flu can trigger pneumonia, and is a bit more serious. Pneumonia is a lung infection caused by either a virus or bacteria. The virus or bacteria cause the tiny sacs inside the lungs to become inflamed and they fill up with fluid or pus. Although there are over 30 causes of pneumonia, according to John Hopkins Medicine, the most common types are:

Bacterial pneumonia: The most common of these is the streptococcus and most often strikes those with low immunity. Young children, the elderly and those with poor nutrition are vulnerable, as are those who have weakened immunity due to excessive alcohol consumption or smoking. Bacterial pneumonia is known to respond to antibiotics.

Viral pneumonia: Differentiated from the above only because it is often caused a virus, sometimes the same one that causes the flu – Influenza A or B. It is very common and is responsible for over 30% of all pneumonia cases. Again, like the flu, it cannot be treated with antibiotics.

Mycoplasma pneumonia: This is the most infectious of them all. That’s why the doctors call it the ‘walking pneumonia’ (the medical term is mycoplasma pneumoniae). The bacteria are known to cause ear infections, chest colds and sore throats, besides pneumonia. Schools, malls, offices – every crowded place has these air-borne bacteria. It is the mildest form of pneumonia and is usually treated with antibiotics. There are rare cases when mycoplasma pneumonia could get serious and could potentially leave a life-altering damage.

When is it time to go to the GP?

Often when people come down with a cold or the flu in winter, they carry on thinking the symptoms will pass. But if the symptoms persist and get more intense, it is time to call the GP. The similarity of symptoms make it impossible to self-diagnose, but if you have any of the following, it could be pneumonia:

  • Cough with green, yellow or bloody mucus
  • Fever and chills
  • Shortness of breath and pain in the chest when breathing
  • Low energy, extreme tiredness or loss of appetite
  • Heavy perspiration and rapid breathing
  • Wheezing when coughing

Testing for pneumonia

The good news is that pneumonia is usually easy to diagnose. Just a physical examination will determine the cause. But to confirm it the GP may order some of these tests:

  • Chest x-ray
  • Blood and sputum tests
  • Chest CT scan
  • Bronchoscopy

There is battery of specialised tests that a GP can recommend if the diagnosis is particularly difficult.

Conditions that are more common or flare-up in colder weather are best identified and treated quickly. So, see your GP today if you are showing any of the symptoms.

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