Cold or Flu: Seven Signs That Help Tell Them Apart

As respiratory viruses spread during the autumn season, many people wonder whether they have an ordinary cold or already the flu. The two illnesses share many symptoms, so how a person feels is not always enough to tell them apart reliably. Still, several signs offer a fairly clear clue about which illness it is.

Seven distinguishing signs

How it starts. A cold usually develops gradually: first a tickling throat or blocked nose, then a runny nose, sneezing and cough, often over one to three days. Flu "switches on" abruptly – within a few hours a person can feel very unwell, with chills, fever, headache and severe exhaustion.

Temperature. Fever is uncommon in adults with a cold, though it may occur in children. For flu, fever and chills are more typical, but a normal temperature does not rule flu out.

Body aches. Pronounced muscle and joint pain points more towards flu, while a cold brings only mild aches.

The nose. A runny, sneezy or blocked nose is more typical of a cold. With flu these may be present but are usually not the main problem.

Energy levels. With a cold, people can often carry on with daily duties, though with less energy. Flu more often causes complete exhaustion and a wish to stay in bed.

Headache. Headaches more often accompany flu. They are less common with a cold, although a blocked nose and pressure in the face can also cause them.

Cough. With a cold the cough is usually milder and often appears together with a runny nose. With flu it may be stronger and frequently dry. The World Health Organization notes that a dry cough can persist for two weeks or longer. This is not a reliable diagnostic criterion, however.

When to seek help

Urgent medical care is needed if there is difficulty breathing or shortness of breath, prolonged chest pain or pressure, confusion, seizures, severe weakness or signs of dehydration. People at higher risk of severe flu should be especially careful: older adults, pregnant women, young children and people with certain chronic conditions.

Antibiotics treat neither colds nor flu, because both are viral infections. In certain situations, a doctor may prescribe antiviral medication for flu.