Cold and the flu: what to know

What’s the difference between a cold and the flu? Who’s at greatest risk of catching a flu virus? Find out the answers to these important questions and many more

The flu at a glance

Cold and the flu: what to know


Influenza (the flu) is caused by a virus, and there are 3 main types of influenza virus:

  • Type A: these viruses are responsible for most cases of the flu in humans. There are many subtypes, eg: H1N1, and some can cause epidemics.
  • Type B: these viruses are less common and usually cause less severe illness. However they can cause outbreaks of the flu - particularly among children.
  • Type C: these viruses usually only cause mild flu and are rare


Flu spreads by inhaling the droplets that are expelled from an infected person's respiratory tract when they talk, cough or sneeze. It can also spread by people touching contaminated surfaces (such as a used tissue or door handle) or other people’s hands, and then touching their own eyes or nose.


Most people start to feel better within a couple of weeks, but for some, the flu can lead to other complications.

What makes flu particularly challenging is that you can infect someone the day before your own symptoms develop, and up to five days after your symptoms appear. This means you could give the flu to someone else before you even know you are unwell.


Flu usually makes people much more unwell than a cold does. Symptoms of flu usually appear 1 to 3 days after exposure.

  • Sudden fever (39C and over)
  • Dry cough
  • Achy muscles
  • Headache
  • Sore throat
  • Extreme tiredness
  • Runny or blocked nose and sneezing
  • Stomach symptoms, such as nausea, vomiting and tummy upsets (more common in children)

Cold and flu: when symptoms seem the same

It is easy to confuse a cold with the flu. Both are respiratory illnesses, and because some of the symptoms are the same - like a runny nose and a sore throat - it can be difficult to tell them apart. Generally, flu symptoms are worse than cold symptoms, and are more likely to affect your whole body, rather than just your nose and throat.

With the flu, you are more likely to have a fever, headache, muscle aches, extreme tiredness and a dry cough. The flu is also more likely to result in other complications.

Cold symptoms are usually mild. With a cold, your main symptom is likely to be nasal congestion or a runny nose.

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