Two schoolchildren are among the latest confirmed cases of swine flu in the UK, bringing the total number to 18.
Both children are from London - the 11-year-old recently returned from America while the 14-year-old had close contact with someone who'd been to Mexico.
One of their schools has now closed for seven days to stop the virus spreading.
Both pupils are said to be responding well to treatment. Meanwhile, more than 700 people are still being tested to see whether they've caught the virus.
So far, swine flu has been detected in at least 18 countries since the outbreak was first detected in Mexico.
The first cases of people catching the bug without having travelled to Mexico were confirmed on Friday.
But British health officials say the risk to the public is still "very low".
The man in charge of health matters for the British government, Alan Johnson, says swine flu in the UK is being confined, contained and treated effectively.
But he warned that more people would probably be found to have the virus as tests results come back over the coming days.
In Mexico, it was thought more than 175 people there may have died from the bug.
But officials have now slashed that number to 101, giving hope that the outbreak may not be as bad as it was feared to be.
Virus expert Professor Wendy Barclay explains more about swine flu
The government there has closed all non-essential services for five-days to try to stop swine flu spreading.
Meanwhile, Chief Medical Officer for England Sir Liam Donaldson has said the UK is well prepared for the outbreak.
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.
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.
If you want more information, get your mum or dad to call 0800 1513513 for recorded information about swine flu. In Scotland, anyone with concerns about the virus can call 08454 24 24 24.