Flu or cold: how to tell the difference?

In winter, your nose starts running and your throat starts scratching, and the question comes up right away: is this an ordinary cold, or is something more serious like the flu on its way? The difference isn’t just academic: the flu can lead to complications, while a cold usually passes on its own. Here is a short guide to telling them apart by symptoms and knowing when to go to a pharmacy or see a doctor.

Flu and cold: how they differ

A cold is an infection of the upper respiratory tract, usually caused by viruses such as rhinoviruses, ECHO viruses or Coxsackie viruses. Symptoms come on gradually: first a scratchy throat, then a runny nose, hoarseness and a mild cough. Fever is low or absent altogether.

The flu is caused by influenza viruses (in many languages the illness is simply called influenza). Symptoms rarely keep you waiting: within a couple of hours, a fever above 38 °C hits, followed by muscle aches, a headache and deep exhaustion. The cough is usually dry and tormenting. This sudden onset and the general “hit by a train” feeling are typical signs of the flu.

The flu can be especially dangerous for children, older adults and people with a weakened immune system, who develop complications more often, including pneumonia.

Cough as the body’s defense reaction

Coughing is not an illness in itself but a reflex that usually can’t be suppressed. The bronchi and trachea clear themselves of mucus, dust and irritating particles that get in with the air you breathe. A strong coughing fit pushes them out through the airways. With a cold cough, harmful waste substances are also expelled by the same route.

Coughing is also protection. If a piece of bread slips into the trachea while you eat, the sensitive mucous membranes notice it immediately: a coughing fit starts and the foreign object is pushed back up. Without this reflex, a blocked airway could lead to choking.

How breathing works

Over 24 hours we breathe in and out about 20000 times, mostly without noticing. Every breath supplies the body with oxygen and carries away the carbon dioxide produced in cells during energy processes.

• When you inhale, the volume of the chest increases with the help of the chest muscles and the diaphragm, and air flows in.
• In the upper respiratory tract, the air is filtered, humidified and warmed.
• The air travels through the pharynx into the trachea and on into the branching bronchi; in the alveoli of the lungs, oxygen is exchanged for carbon dioxide.
• When you exhale, the chest muscles and the diaphragm relax.

With a cold or the flu, the mucous membrane of the upper respiratory tract is exactly where the immune system has the hardest job to do. We are more susceptible when the body is weakened by stress or exhaustion, when there are plenty of pathogens around (coughing, sneezing, shared objects), or when the mucous membrane is already inflamed because of allergy. Protection is also temporarily weaker after the tonsils have been removed.

The phases of a cough during a cold

Phase 1: irritating cough. At the start of the illness the cough is dry and tormenting, with little mucus; this is a non-productive cough. It is especially strong at night. The mucous membranes are inflamed and coughing hurts.

Phase 2: congested cough. With a stronger cold, the mucous membrane begins to produce thick mucus. The cough becomes “loose,” or productive, but the secretion often stays stuck in the bronchi and upper respiratory tract and is hard to cough up. The cough is exhausting and painful.

Phase 3: expectorants. Pharmacies sell preparations (for example acetylcysteine, or ACC) that make thick mucus thinner and more mobile, so it becomes easier to cough up.

Phase 4: when the cough doesn’t go away. The causes of a long-lasting cough can range from a simple infection to serious illness. If the cough drags on for more than 3 weeks, or if you start coughing up blood, or have shortness of breath or a high fever, you must see a doctor. An X-ray and a blood test provide reassurance.

When the flu needs a doctor’s attention

A healthy adult can usually get over both a cold and a mild case of the flu at home. Bed rest, plenty of fluids and, if needed, a fever reducer usually do the job. But if breathing becomes difficult, the fever stays above 39 °C for several days, or you get severe chest pain, don’t hesitate to call your family doctor or the family doctor advice line 1220.

In risk groups — young children, people over 65, pregnant women and people with chronic illnesses — the flu can quickly become complicated. In their case, it’s worth asking for advice as soon as symptoms begin rather than waiting until things get worse.

FAQ about the flu and colds

How long does the flu last compared with a cold?

A cold usually passes in 7–10 days. The acute phase of the flu lasts 5–7 days, but fatigue and cough can drag on for several weeks.

Do antibiotics help against the flu?

No. Both colds and the flu are caused by viruses, and antibiotics work only on bacteria. A doctor prescribes them only if a bacterial complication, such as pneumonia, is added to the viral infection.

How can you protect yourself from the flu?

Wash your hands often, avoid touching your face and keep your distance from people who are sick. Risk groups should consider getting vaccinated against the flu every year — it doesn’t protect against colds, but it significantly reduces the severity of the flu and the risk of complications.

Author: Marek Morozov

Source: WHO – physical activity.

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