Cold or Flu? How to Tell the Difference

A runny nose, cough and tiredness could be a cold or flu. Both are caused by viruses and both spread through coughs and sneezes. Telling them apart is not always easy, but a few clues can help. This article compares the two using guidance from the NHS and the CDC.

How quickly do symptoms start?

The NHS says a cold builds up gradually over a couple of days, while flu symptoms come on very quickly, often within a few hours. If you were well in the morning and feel awful by the afternoon, flu is more likely than a cold. Only a doctor can say for sure what you have.

Which parts of the body are affected?

A cold mainly affects the nose and throat, according to the NHS. Flu affects more than that. The NHS lists these flu symptoms:

• A sudden high temperature
• An aching body
• Tiredness or exhaustion
• A dry cough, sore throat or headache
• Difficulty sleeping or loss of appetite

The CDC adds that not everyone with flu has a fever, and that vomiting and diarrhoea are more common in children than in adults. In children, the NHS says flu can also bring ear pain, sore eyes, swollen glands and being less active than usual.

Cold symptoms listed by the NHS include a blocked or runny nose, sneezing, a sore throat, a hoarse voice, a cough and feeling tired and unwell.

How severe do you feel?

With a cold, the NHS says you can usually keep going with normal activities, such as work. With flu, you may feel too exhausted or unwell to do your normal activities. COVID-19 can also look like a cold or flu, with a cough, tiredness, body aches, headache and sore throat, so a doctor or a test may be needed to tell them apart.

Who is at higher risk of serious flu?

Anyone can become seriously ill with flu, including healthy people, says the CDC. The NHS and CDC list these groups as higher risk:

• Adults aged 65 or over
• Pregnant people, and those who have recently given birth
• Young children (the CDC mentions children under 5, especially under 2)
• People with long-term conditions such as diabetes, or heart, lung, liver, kidney or nerve conditions, or asthma
• People with a weakened immune system

What helps at home?

For both illnesses, the NHS suggests rest, plenty of fluids and staying home if you have a high temperature or feel too unwell for normal activities. A pharmacist or doctor can advise on suitable medicines for aches and fever. Antibiotics do not work on viral illnesses, as both the NHS and CDC explain. The NHS also says not to give aspirin to children under 16.

To avoid spreading either illness, wash your hands often, cover your mouth and nose when you cough or sneeze, and bin used tissues quickly. The NHS says the flu vaccine does not protect against colds.

When to see a doctor

For a cold, the NHS advises seeing a doctor if symptoms last more than 10 days, a fever lasts more than 3 days, symptoms get worse, you have shortness of breath or chest pain, or you have a long-term condition or weakened immune system.

For flu, the NHS advises getting urgent advice if you feel very unwell or short of breath, symptoms have not improved after 7 days, you are worried about a baby or child, or you are in a higher-risk group.

The CDC lists these emergency warning signs in adults:

• Trouble breathing or shortness of breath
• Persistent chest or stomach pain or pressure
• Ongoing dizziness, confusion or inability to stay awake
• Seizures or not passing urine
• Severe muscle pain or weakness
• A fever or cough that improves and then comes back worse

In an emergency, call your local emergency number (112 in India, 911 in the United States).

This article is general education and cannot replace a doctor's advice.