Watch the government's Swine Flu advert
A new TV advert is being launched to try to stop swine flu spreading any further in the UK.
It's been put together by the government, and shows the importance of using tissues when you sneeze and washing your hands afterwards.
Late on Wednesday the World Health Organisation (WHO) said it expected the spread of swine flu to get worse.
The WHO says it now knows that the bug has spread from person to person in two different countries.
On Wednesday doctors said that a 12-year-old girl is one of five people in the UK that has swine flu.
She had recently been on holiday in Mexico.
Her school in Paignton, Devon, has been closed to avoid the disease spreading and pupils are being offered medicine to cut the chance of them getting sick.
It's thought about 168 people in Mexico may have died because of the virus.
In the UK, the 12-year-old girl, three men and one woman are the only people who've been confirmed as having swine flu and all are said to be responding well to treatment.
Tests are being carried out on loads more people across the country to find out if they're just ill or if they've also got caught the virus.
UK well prepared
Lots of the symptoms of swine flu are like ordinary flu - a fever, feeling tired, coughing and having a sore throat.
But even if you have all these symptoms, it's REALLY UNLIKELY
you have swine flu as it's still very unusual in the UK.
Virus expert Professor Wendy Barclay explains more about swine flu
Doctors who have studied the virus say it's like other types of flu, but has bits mixed into it from the flu bugs that pigs and birds can catch.
Medicine that's used to treat ordinary flu has been helping people with swine flu to get better and scientists are working on a new drug that could stop people catching the bug in the future.
The government says it's really well prepared for the outbreak - it's been stocking up on flu medicine for years and has enough to treat millions of people.
Meanwhile, there are still lots of British people on holiday in Mexico - where swine flu was first found - and they are being checked as they come back to the UK.
Some holiday companies have also cancelled trips to Mexico, and the government's foreign office is recommending that people don't go to the country unless they have to.