The swine flu virus is spread in exactly the same way as the ordinary cold and flu viruses.

However, because few people, if any, have full resistance to the new strain, they are much more likely to become infected once they come into contact with the virus.

The virus is contained in the millions of tiny droplets that come out of the nose and mouth when someone coughs or sneezes.

These droplets typically spread about one metre (3ft). They hang suspended in the air for a while, but then land on surfaces, where the virus can survive for up to 24 hours.

Anyone who touches these surfaces can spread the virus on further by touching anything else.

Everyday items at home and in public places may have traces of the virus. These include food, door handles, the remote control, hand rails and computer keyboards.

People usually become infected by picking up the virus on their hands from contaminated objects and then placing their hands near their mouth or nose. It is also possible to breathe in the virus if it is suspended in airborne droplets.

Good hygiene

Preventing the spread of germs is the most effective way to slow the spread of diseases such as swine flu. You should always:

• ensure everyone washes their hands regularly with soap and water,
• clean surfaces regularly to get rid of germs,
• use tissues to cover your mouth and nose when you cough or sneeze, and
• put used tissues in a bin as soon as possible.

Resistance and mutation

If you become infected with a flu virus, your body will produce antibodies against it. This will recognise and fight off the virus if your body comes across it again.

However, the swine flu virus is a new virus that few people, if any, have resistance to. It is possible that some older people may have some resistance from being exposed to a similar virus in a previous pandemic.

Viruses typically mutate (change) into different versions and develop resistance to medicines, including antivirals.

A case of swine flu resistance to Tamiflu has been reported in the UK.

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