Swine flu (also known as H1N1) is a new strain of the influenza virus which attacks the upper and lower airways. It is one of the Type A influenzas, which cause mass pandemics and the most serious symptoms.

It probably originated in pigs in Asia, but it is now uniquely a human disease. It is spreading very quickly throughout Britain.

The Health Protection Agency estimates that there were 100,000 new cases of swine flu in England last week.

Anyone can catch swine flu, but the majority of cases are mild — many people may already have had swine flu without even knowing it.

Those with symptoms tend to recover fully within a week.

But certain people are more at risk of getting swine flu and developing complications as the virus enters the lungs.

Those most at risk include:

Children up to the age of 14 — this age group has the highest rate of infection;

Babies under the age of one are at particular risk of complications as they have underdeveloped immune systems;

The over-65s have the lowest rate of infection, probably because they've been exposed to previous pandemics and have an immunity;

Pregnant women — their immune systems are less effective. This is so their bodies don't reject their growing babies, but it does make them more vulnerable to swine flu and complications. They are most at risk in the third trimester;

Those who suffer from conditions affecting the airways — this includes asthma and chronic obstructive pulmonary disease (COPD); the flu virus can attack the lungs, making it more difficult to breathe.

People with neurological diseases (such as Parkinson's); chronic heart disease; chronic kidney disease; diabetes; lowered immune systems (as a result of HIV/Aids);

Obese people — they are more likely to suffer complications because many already suffer from respiratory problems such as COPD and/or diabetes.

Stock up on flu medications containing paracetamol, which can help to relieve the high fever often associated with flu.

Make sure you have several people who agree to act as your 'flu friend' — the nominated person who will pick up your medication/Tamiflu. If you have only one flu friend, there is a risk they will get flu when you do and won't be able to pick up your medicine.

Although Tamiflu can act as a preventative, you would have to take it every day throughout an outbreak for it to be effective and it has not been shown that it is safe to take for longer than six weeks.

Have a thermometer handy. An old-fashioned mercury thermometer is fine for adults, but for children use a digital thermometer (placed in the mouth or under the arm), or an ear thermometer (more accurate, but expensive).

Take our test and then check your symptoms with the National Pandemic Flu Service website, www.pandemicflu.dir ect.gov.uk.

This should be able to confirm whether you are likely to have the flu.

Call your GP directly if:

You have a serious underlying illness;

You are pregnant;

You have a sick child under one year old;

Your condition suddenly gets much worse.

Your condition is still getting worse after seven days (or five days for a child);

Anyone else should stay at home — do not go to your GP if you think you have swine flu because this could spread the disease, which is especially dangerous for those who already have other health problems.

At the moment, everyone who contacts the National Pandemic Flu Service and who is deemed to have swine flu will get an authorisation number which can be used to collect antiviral medication from a local collection point.

For those who do not have internet access, the same service can be accessed by telephone: 0800 1 513 100, or 0800 1 513 200.

Callers to the National Pandemic Flu Service will be asked questions to determine if the symptoms are due to meningitis rather than swine flu.

However, it's possible people with tonsillitis and Strep A infection will incorrectly be told that they have swine flu.

While tonsillitis can also cause fever, headache and chills, just like flu, a tell-tale sign is when the tonsils are red and inflamed and covered with white patches. It will also be difficult and painful to swallow.

Strep A symptoms include sore throat, fever and earache, but also possibly bright-red tonsils and a sandpapery rash on the arms and trunk.

Anyone who is concerned that they may be suffering from an illness other than swine flu should contact their GP directly.

Make sure you drink plenty of fluids and get lots of rest. Medications containing paracetamol are useful in helping to bring down fever and reduce pain.

Antivirals available include Tamiflu and Relenza. Both are equally effective and need to be taken within the first 48 hours of symptoms appearing.

Tamiflu is the most commonly prescribed and is given as capsules or in liquid (for children).

Suitable for anyone aged over one, it treats the symptoms of swine flu by stopping the virus from replicating and leaving infected cells.

Relenza is taken as an inhaler and is delivered directly to the airways where it is needed. It works in the same way as Tamiflu, stopping the spread of infection.

Relenza is the first choice for pregnant and breast-feeding women, but it is not suitable for people who suffer from respiratory problems because it can cause the airway to spasm.

Antibiotics do not tackle flu itself, but they can help to limit the spread of secondary infections in your lungs.

Your doctor will prescribe them if necessary via a phone consultation, so you don't have to go into the surgery.

A swine flu vaccine is being developed and the first batch is expected to be available by late August or early September.

The first people to have the vaccine were given it this week in Australia.

When it is ready for general use, everybody will need two jabs.

The Department of Health said: "We have not decided how the vaccination programme will work, but it would seem sensible that those at risk, such as people with underlying chest problems, pregnant women and, possibly, healthcare workers, will receive the vaccine first."

If you come into contact with someone who has swine flu, or you are looking after someone who is ill, there is no need to isolate yourself — you can carry on as normal unless you develop the symptoms.

You will not be given antivirals as a preventative.

If you or one of your family becomes ill it is a good idea for them to stay in a separate section in the house, especially if there are any young children or pregnant women in the household.

If this is not possible, keep at least one metre away from others.

Carers should wash their hands after contact with you. Keep windows open to encourage air circulation.

Adults are infectious for around five days — from a day before symptoms begin, and while the symptoms are at their worst.

Children may be infectious for up to a week.

But you should stay at home until all the symptoms have disappeared and you are fully recovered and fit to work.

This could be a week or longer after the initial symptoms appeared.

You cannot get swine flu twice because your body will have built up resistance to the infection.