Cough Caused by a Virus

Authored by , Reviewed by Dr Hayley Willacy | Last edited | Meets Patient’s editorial guidelines

Most coughs are caused by viral infections and usually soon go. This leaflet gives some tips on what to do and which symptoms to look out for that may indicate a more serious illness. Viral infections commonly affect the throat (larynx), or the main airway (trachea), or the airways going into the lungs (bronchi). These infections are sometimes called laryngitis, tracheitis, or bronchitis. Cough is often the main symptom.

The cough typically develops over a day or so and may become quite irritating. Other symptoms may develop and include high temperature (fever), headache, aches and pains. Cold symptoms may occur if the infection also affects the nose. Symptoms typically peak after 2-3 days, and then gradually clear. However, the cough may persist for up to four weeks after the infection has gone. This is because the inflammation in the airways, caused by the infection, can take a while to clear.

Cough caused by COVID-19 infection

This leaflet is being written during the COVID-19 pandemic and at the time of writing we don't know how long COVID-19 needs to be considered as an important cause of cough.

Apart from a new continuous cough, other symptoms may include:

  • A high temperature.
  • A loss or change to your sense of taste or smell.

See our separate editorial content called Coronavirus: what are asymptomatic and mild COVID-19? and Coronavirus: what are moderate, severe and critical COVID-19? for more details.

The rest of this leaflet is about coughs which are not caused by the coronavirus.

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There is no 'quick fix' for a cough due to a viral infection. You need to be patient until the cough goes. A main aim of treatment is to ease symptoms whilst your immune system clears the infection. The most useful treatments are:

  • Taking paracetamol, ibuprofen, or aspirin to reduce high temperature (fever), and to ease any aches, pains and headaches. (Children aged under 16 years should not take aspirin.)
  • Having lots to drink if you have a fever, to prevent mild lack of fluid in the body (dehydration).
  • Stopping smoking. If you smoke, you should try to stop for good. A cough and serious lung diseases are more common in smokers.

What about cold and cough remedies?

You can buy many other cold and cough remedies at pharmacies. There is little evidence of any impact on the infection but they may be useful for certain symptoms. For example, a decongestant nasal spray may help to clear a blocked nose.

But remember, cold and cough remedies often contain several ingredients. Some may make you drowsy. This may be welcome at bedtime if you have difficulty sleeping with a cough. However, do not drive if you are drowsy. Some contain paracetamol, so be careful not to take more than the maximum safe dose of paracetamol if you are already taking paracetamol tablets.

In March 2009 an important statement was issued by the Medicines and Healthcare products Regulatory Agency (MHRA) which says:

"The new advice is that parents and carers should no longer use over-the-counter (OTC) cough and cold medicines in children under 6. There is no evidence that they work and they can cause side-effects, such as allergic reactions, effects on sleep or hallucinations.

For 6 to 12 year-olds these medicines will continue to be available but will only be sold in pharmacies, with clearer advice on the packaging and from the pharmacist. This is because the risk of side-effects is reduced in older children because they weigh more, get fewer colds and can say if the medicine is doing any good. More research is being done by industry on how well these medicines work in children aged 6-12 years."

Note: paracetamol and ibuprofen are not classed as cough and cold medicines and can still be given to children. 

What about antibiotic medicines?

Antibiotics are not usually advised. Antibiotics do not kill viruses - they only kill germs called bacteria. Antibiotics do not usually ease a cough caused by a virus. They may even make symptoms worse, as they sometimes cause side-effects such as loose or watery stools (diarrhoea), feeling sick, and rashes.

Antibiotics may be prescribed if you already have an ongoing (chronic) lung disease. This is to prevent a 'secondary' bacterial infection rather than to clear a viral infection. Antibiotics may also be prescribed if a complication develops such as secondary bacterial pneumonia - but this is unlikely to occur if you are otherwise healthy.

How can I tell if my cough is viral or bacterial?

This may not be easy in the early stages as cough is a common symptom of both viral and bacterial infections. A viral infection of the upper respiratory system (in other words a common cold) often causes nasal symptoms such as a stuffy nose and sneezing which clear up after a few days. Though the cough may persist for up to four weeks, you generally start to feel better as the days go by. If you start to feel worse, this is one sign that you may have a bacterial infection. Other features suggesting that you may be developing a bacterial infection are a fever above 38°C and coughing up thick discoloured phlegm. You may develop chest pain, rapid breathing, and/or rapid pulse. Wheezing and difficulty in breathing may be other signs.

How long will I remain infectious?

If you have a viral infection like a common cold, you can pass it on to other people for as long as your symptoms persist. You are most infectious in the first two days. Most people are clear of infection after about two weeks.

Most viral coughs clear without complications. However, sometimes a 'secondary' infection with germs (bacteria) develops in addition to the viral infection. This may become serious and cause pneumonia. Also, other causes of cough (such as asthma) are sometimes confused with a viral infection. So, see a doctor if any of the following occur.

  • If you develop symptoms of a possible bacterial infection, as described above.
  • If you cough up blood. Blood may be bright red but dark or rusty-coloured sputum may indicate blood.
  • If you become drowsy or confused.
  • If you develop any symptoms which you are unhappy about, or do not understand.
  • If you have a cough that persists for longer than 3-4 weeks.

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Further reading and references