Flu and Flu-Like Illnesses

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What are flu and flu-like illnesses?

Influenza (flu) is caused by the influenza virus. However, many other viruses can cause an illness similar to flu. It is often difficult to say exactly which virus is causing the illness. Therefore, doctors commonly make a diagnosis of a 'flu-like illness'.

Each winter a different strain of the influenza virus causes an outbreak of flu which affects many people. During an outbreak of flu, if you get a 'flu-like' illness it is more likely to be caused by the influenza virus than by another type of virus. Note: bird flu (avian influenza) is different to the usual 'human' flu and is more serious. See separate leaflet called Bird Flu for details.

What are the symptoms of flu or a flu-like illness?

Typical symptoms in adults and older children include: high temperature (fever), sweats, muscle aches, a dry cough, sore throat, sneezing, and headache. You may also feel sick. The flu illness caused by the influenza virus tends to be worse than illnesses caused by other viruses which cause a 'flu-like' illness. Even if you are young and fit, flu can make you ill enough to need to go to bed.

Symptoms in babies and young children can include: high temperature (fever), sweats, a cough, sore throat, sneezing, difficulty in breathing, lethargy, poor feeding. Some young children have a febrile convulsion when they have flu.

Symptoms peak after 1-2 days, and then usually gradually ease over several days. An irritating cough may persist for a week or so after other symptoms have gone. Most people recover completely within 1-2 weeks.

What else could my symptoms be due to?

Other serious illnesses can have similar symptoms to flu when they first develop. For example, meningitis, malaria, or pneumonia. If you have a more serious illnesses, additional symptoms usually develop in addition to those mentioned above. Symptoms to look out for which may mean that you have a different and more severe illness include:

• Rash - in particular if dark red spots develop that do not fade when pressed.
• Stiff neck - particularly if you cannot bend your neck forward.
• A headache that becomes worse and worse.
• Dislike of bright lights - if you need to shut your eyes and turn away from the light.
• Drowsiness.
• Confusion.
• Repeated vomiting.
• Chest pains.
• Coughing up blood or blood-stained sputum.

Note: also, tell a doctor if you have flu-like symptoms, but you have been to a country within the last year where malaria is present. Symptoms of malaria can be similar to flu at first.

What is the treatment for flu and flu-like illnesses?

Your immune system will usually clear viruses that cause flu and flu-like illnesses. Treatment aims to ease symptoms until the infection goes.

• Paracetamol or ibuprofen will lower your temperature, and ease aches and pains.
• Have lots to drink to prevent dehydration (low body fluid).

Antiviral drugs
Antiviral drugs called Zanamivir and Oseltamivir are sometimes used for flu. They do not kill the virus but interfere with the way the virus multiplies. Therefore, they do not cure flu, but may reduce the severity and duration of symptoms, and may prevent complications. If you develop flu, an antiviral drug may be prescribed if you are at increased risk of developing complications. Antiviral drugs need to be given soon after symptoms begin to be of any benefit. Also, an antiviral drug may be prescribed to certain people to prevent flu. For example, if you live in a residential home and there is an outbreak of flu in the home. Or, if you are at increased risk of complications and have been in close contact with a person with flu.

What are the possible complications of flu and flu-like illnesses?

If you are normally well, then you are unlikely to develop complications. You are likely to fully recover. However, see a doctor if symptoms change or become worse. Complications are more likely to develop if you are in any of the 'at risk' groups listed below.

The most common complication is a 'secondary' bacterial chest infection which may develop in addition to the virus infection. This can sometimes become serious and develop into pneumonia. A course of antibiotics will usually cure this. However, a secondary bacterial infection can sometimes becomes life-threatening, particularly in the frail and elderly. But note: with flu or a flu-like illness it is common to have a cough that lingers for 1-2 weeks after other symptoms have gone. Green sputum does not necessarily mean that you have a secondary chest infection. The symptoms to look out for that may indicate a secondary chest infection include: a recurrence of a high temperature, worsening of cough, shortness of breath, fast breathing, chest pain.

Other complications that sometimes occur include a sinus infection and an ear infection. Rarely, other serious complications such as brain inflammation (encephalitis) develop.

Who should be immunised against the influenza virus?

The Department of Health issues advice as to who should be immunised. This is reviewed from time to time. The aim is to protect people who are more likely to develop complications from flu. Current advice is that you should be immunised against the influenza virus each autumn if you:

• Are aged 65 or over.
• Have a chronic (ongoing) lung disease. For example: chronic obstructive pulmonary disease (COPD), emphysema, chronic bronchitis, asthma which requires regular use of inhaled steroids or steroid tablets (or if you have previously been admitted to hospital because of asthma), cystic fibrosis, interstitial lung fibrosis, pneumoconiosis, etc.
• Are a child who has previously been admitted to hospital with a lower respiratory tract disease such as pneumonia.
• Have a chronic heart disease. For example: if you require regular medication or follow-up for ischemic heart disease (angina, heart attacks, etc), congenital heart disease, chronic heart failure, hypertensive heart disease (not uncomplicated high blood pressure that is controlled with medication).
• Have a serious chronic kidney disease. For example: nephrotic syndrome, kidney failure, if you have had a kidney transplant.
• Have chronic liver disease such as cirrhosis.
• Have diabetes which requires insulin or tablets to control it.
• Have a poor immune system. (For example, if you have no spleen, are taking chemotherapy or steroid treatment, if you have HIV/AIDS, etc.)
• Live in a nursing home or other long stay residential care accommodation.

Also, you should have the flu jab if you are the main carer of an elderly or disabled person whose welfare may be at risk if you fall ill. (For example, if you were to develop flu.) Also, healthy staff involved in direct patient care may be offered a flu jab from their employer.

If you are healthy and under 65 and do not fall into any of the above categories, then you do not need a flu immunisation. This is because you are unlikely to develop complications from flu.

The influenza virus gives good protection against the influenza virus, and lasts for one year. The vaccine is normally ready by the autumn each year. It is made from the strain of influenza virus that is expected in the coming winter. You need a yearly immunisation to keep protected.

See separate leaflet called 'Influenza Immunisation' for more details.

© EMIS and PIP 2006   Updated: October 2006   PRODIGY Validated

The authors and editors of this article are employed to create accurate and up to date content reflecting reliable research evidence, guidance and best clinical practice. They are free from any commercial conflicts of interest. Find out more about updating.

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