You may think flu is just a worse version of a cold, but it's important to recognise the symptoms of both

Many people confuse the terms 'cold' and 'flu' because the illnesses share some of the same features. Both are caused by viruses that infect the respiratory tract, mainly in the winter season, and both can cause symptoms such as coughing and sore throat. But here the similarity ends...

A cold is a minor viral or bacterial infection of the nose and throat and can occur in any season. Unlike treatment for flu, seeing your doctor when you have a cold is unnecessary for most healthy people, unless your illness exceeds 10 to 14 days. If it persists beyond this time you should see a GP to rule out a secondary infection, such as sinusitis or bronchitis.

The flu, short for influenza, is a viral disease of the respiratory tract - the nose, throat, bronchial tubes and lungs - and is highly contagious. It is spread through airborne droplets of moisture produced by coughs or sneezes.

When you breathe these germs in through your nose or mouth, you may come down with the flu, generally within one to three days of being exposed. There are two main types of 'flu: Type A and Type B, of which Type A tends to be most severe.

The influenza virus mutates easily so that immunity from a previous vaccination does not fully protect against it. The immune system tends to make antibodies directed at two antigens on the surface of the virus: haemagglutinin (H) and neuraminidase (N). Changes in the shape of these two antigens means that pre-formed antibodies are less likely to lock on to them. The world therefore experiences new strains of influenza virus relatively frequently.

Recognising the symptoms
The flu's symptoms come on suddenly and include a high fever of 38 to 40 degrees Centigrade, headache, often severe aches and pains, tiredness, weakness and chest discomfort or coughing. Sometimes it involves a stuffy nose, sneezing and sore throat.

A cold, on the other hand, rarely causes more than a mild fever, headache, extreme exhaustion or aches and pains. Its most obvious symptoms are a stuffy nose, sneezing, sore throat and a mild to moderate cough.

Older people are more susceptible to contracting influenza and suffering from its potential complications, as are children, people with compromised immune systems, and individuals with chronic illnesses such as heart disease, kidney disease and diabetes.

In addition, the risk for respiratory infections is increased by exposure to cigarette smoke, which can injure airways and damage the cilia, the tiny hair-like structures that help keep the airways clear. Toxic fumes, industrial smoke and other air pollutants also are risk factors.

Complications
The most serious, often life-threatening complication of the flu is pneumonia. Other complications include ear infection, bronchitis, chronic lung disease and fever-related convulsions. Croup and a lung disease called bronchiolitis can arise as complications in infants and young children.

The good news is that the flu is preventable if you get vaccinated. Because the influenza virus changes its genetic make-up from year to year, you're most likely to be exposed to a new virus. That's why you can get the flu every year,a new flu jab is recommended every year. If you?re aged 65 or over, or have a serious medical condition (eg asthma, diabetes, chronic heart, chest or kidney complaints, lowered immunity) it is important to receive your annual vaccination against influenza. Contact your local GP surgery for details, ring NHS Direct on 0845 4647, or visit www.immunisation.nhs.uk

Modern treatments
Scientists have a new weapon in their arsenal to fight influenza. This new class of drugs, called neuraminidase inhibitors (NAI), attacks the influenza virus at the cellular level and blocks the viruses' ability to escape from cells that they have already infected, thereby preventing the infection from spreading. These include a nasal powder spray called zanamivir (Relenza) and capsules containing oseltamivir (Tamiflu) which can shorten the duration of flu by one to three days and reduce complications, including pneumonia and bronchitis. In the UK, these drugs are only used to treat at-risk individuals who can start treatment with 48 hours of close contact with a flu-like illness.

Diagnosing flu
The flu causes muscle and joint pain, high fever, chills, fatigue and weakness that usually send the afflicted straight to bed for three to five days or longer. Afterwards, your cough and tiredness may persist for days or even weeks. Other symptoms include headache, eye pain and sometimes a stuffy nose and sore throat. Upset stomach, vomiting or diarrhoea are rarely major features of the flu.

Since complications from influenza are more likely to develop the longer you have the virus, seeking medical attention and an accurate diagnosis quickly is your best bet for getting back on your feet as soon as possible.

Recognising pneumonia
Pneumonia symptoms typically appear after you start feeling like you're recovering from the flu. A brief period of improvement followed by the sudden onset of the following symptoms may indicate you've developed pneumonia:

• High fever
  
• Shaking chills
  
• Chest pain with each breath
  
• A continuous hacking cough that produces thick, yellow-greenish-colored phlegm
  
• Extreme weakness and fatigue. A chest x-ray will detect the disease and a combination of antibiotics and intravenous drip may be required

Acute bronchitis, another complication of the flu, is an inflammation of the bronchi, the air passages or tubes to the lungs - not of the lung tissue itself as in pneumonia. Acute bronchitis often follows a common cold or flu or any infection of the nose and throat, usually for the same reason as pneumonia, i.e. your defences are lowered, making you more susceptible to the viruses or bacteria that cause these illnesses.

Bronchitis has the following symptoms:

• A slight fever, 37 to 39 degrees Centigrade
  
• An irritating, dry and painful cough that starts to produce thick, yellow sputum after two or three days; at this stage the fever often recedes and the pain from coughing diminishes
  
• Most bronchitis is caused by a virus, so doctors will not usually advise antibiotics unless a secondar bacterial infection is suspected.

Treating flu
Because the flu is a viral infection, it cannot be treated with antibiotics. Antibiotics only kill bacteria and thus are useless against the flu. Taking antibiotics when you don't need them contributes to an important public health problem - antibiotic resistance.

Some diseases that were once easily cured by antibiotics have become resistant to eradication. For example, earlier this century, antibiotics nearly eliminated dreaded bacterial diseases like tuberculosis and gonorrhea. However, years of widespread misuse have allowed 'antibiotic-resistant' forms of these illnesses to become more common. Most people think that taking an antibiotic cannot hurt them. But taking an antibiotic when it will not help, such as for a cold or the flu, can actually increase your risk of getting a bacterial infection that may not be curable.

However, if you've developed a bacterial infection, such as pneumonia, bronchitis or sinusitis, antibiotics may be prescribed. Rest is also important to help you get better. Plus, if you stay at home, there's less risk that you'll give the flu to other people.

The following may help you minimize flu symptoms and recover as soon as possible:

• Rest in bed and stay warm but make sure your room is well ventilated
• If you live alone, arrange for someone to check on you regularly
• Drink plenty of warm fluids which may relieve the feeling of congestion and loosen
• Try to eat a simple diet such as soup, yoghurt or scrambled eggs on bread
• Steam inhalations will help to ease congestion
• Paracetamol or ibuprofen will help to relieve aching and reduce fever
• Take a cough suppressant for relief from a dry, hacking cough when trying to sleep

Seek medical advice if you develop chest pain or difficulty breathing, immediately.

If influenza symptoms develop in the very young, the elderly, or in someone with lung, kidney, heart or other serious problem, contact a doctor straight away. In some cases, an antiviral drug may be needed to reduce the risk of complications, and this needs to be started as soon as possible.

Other methods of reducing symptoms include using a humidifier or steamer to help ease congestion. An over-the-counter decongestant can be taken if you have a stuffy nose, but this symptom is not usually common in influenza. Side effects of oral decongestants can include drowsiness, dizziness, insomnia or upset stomach. There can be a 'rebound' effect with nasal spray decongestants, which means you will require more medication to control symptoms as time goes on, and when you stop using them your stuffiness may come back.

Frequently asked questions
1. Why should I get a flu jab? Isn't there a chance it could give me the flu?
A flu vaccination is your best chance to protect yourself against the flu; it has a 60-90 per cent success rate in healthy adults and children. The vaccine can cause side effects, including fever, tiredness and sore muscles; these symptoms are not influenza itself but an immune response to the virus proteins in the vaccine.

2. I feel awful; why won't my doctor prescribe me some antibiotics?
Because the flu is a viral infection, it cannot be treated with antibiotics. Antibiotics only kill bacteria and thus are useless against the flu. Taking antibiotics when you don't need them contributes to antibiotic resistance.

3. When I blow my nose, the mucus is greenish; doesn't this mean I have an infection and need antibiotics?
A 'green' runny nose is not necessarily an indication of a bacterial infection. Antibiotics only fight bacterial infections. However, you should check with your doctor.

4. When do I need to call my doctor?
The longer you're sick with the flu, the more damage it causes and the higher your risk of bacterial complications. So it's important to call your healthcare professional if you develop these hallmark flu symptoms:

• Sudden onset of illness
  
• An illness so bad you feel entirely drained and immobile
  
• A high and persistent fever
  
• Severe aches and pains, which can include headache
  
• Fatigue and weakness that persists
  
• Chest pain
  
• Coughing up thick or discolored mucus
  
• Facial swelling or pain
  
• Earache