Flu vs a cold: what's the difference?

To help you differentiate between the three illnesses Dr Sam Rodgers explains the symptoms of each illness to look out for.

​We are more susceptible to colds and flu in winter in the UK - from around November to March. Although they are caused by different viruses, they share similar symptoms. So how can you tell the difference between them?

The common cold is more likely to start with a sore throat and the flu will often begin with a cough and then follow with a fever – as told by the Centres for Disease Control and Prevention (CDC).

To help you differentiate between them, we explain the symptoms of colds and flu.

What's the difference between a cold and the flu?


The best way to distinguish between whether you have a cold or the flu is to look at your symptoms. A runny nose, headache, sore throat, coughing, and sneezing are classic cold symptoms. Flu symptoms include a dry cough, high temperature, sore throat, chills, muscle aches, and severe fatigue.

The common cold and the flu are respiratory illnesses caused by a viral infection. When an infected person sneezes or coughs, water droplets are released from the nose or mouth that contain contagious viral particles. If droplets land on a surface, they contaminate it, easing the transmission of the virus to others.

Why do more people seem to catch a cold or the flu during winter?


The influenza viruses that cause the flu can spread through the air. It is thought that in cold weather, the influenza viruses are more stable, as they contain an outer lipid membrane which becomes tough when cold. This increases the likelihood of the virus infecting others as viral particles are more active and resilient.

The low humidity experienced during winter also encourages the viruses to float in the air in little droplets. When the air is more humid, those droplets pick up water, increase in size and are quicker to fall to the ground. The viruses capable of causing a cold also thrive in low humidity.

How do I know if it's a cold?


Most colds tend to stay in the upper airways.

You are most likely to have:

  • A blocked nose
  • A sore throat
  • Sneezing

The mucus produced when you have a cold can lead to a cough. Otherwise, you will probably feel okay, just a little run down with aches and pains.

There are 200 different viruses known to cause colds, many of which belong to the rhinovirus family. Most colds will go away by themselves in a week or so without treatment. You can take over-the-counter medicine to relieve symptoms.

How can I tell it's the flu?


The flu, also known as influenza, can be more serious than just a cold and can cause complications such as pneumonia in vulnerable people.

Common symptoms of the flu:

  • A dry cough
  • Aches and pains
  • Fever
  • Fatigue
  • Headaches

Caused by several different influenza viruses, it can affect both the upper and lower respiratory system and tends to last a week or two - though the fatigue may persist a bit longer.

Some people can experience a runny or blocked nose or a sore throat, however, there usually isn’t sneezing or shortness of breath with the flu and the NHS notes there is usually a rapid onset of symptoms.

Each year the NHS offers people at risk of complications a free flu vaccine. This year even more people will be eligible for the free flu vaccination. You can check if you fall into this category here. If you are eligible it is best to get the vaccination in the autumn before flu season starts. Read our blog: how to reduce your risk of flu for more information.

Are there ways to avoid catching a cold or the flu?


Wash your hands regularly, especially before eating, sanitise surfaces and dispose of tissues immediately rather than leaving them lying around. Getting enough sleep is also important to keep the immune system healthy, as is staying hydrated and eating plenty of fresh fruit and vegetables to provide the body with essential vitamins and minerals.

There are many different viruses able to cause a cold so there is no vaccine to prevent you from catching a cold, but there is a flu vaccine. Because different influenza strains are constantly emerging, there is a new flu vaccine every year. The vaccine does not provide 100% immunity but will greatly reduce your chances of getting flu.

A raised white blood cell count and a low platelet count can be indicative of a viral infection present in the body. Our Full Blood Count gives you the ability to see if your blood cell count is raised. 

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