World health chiefs are getting more worried about swine flu after deciding the virus is now a pandemic.
That means it's spreading widely in a number of communities around the world, NOT that it's getting more serious and is a bigger risk to people who get it.
It is the first global flu pandemic for 40 years.
But officials say there's no need to panic as most people with swine flu have mild symptoms and Britain has huge stocks of anti-flu medicine ready.
The number of cases are rising in a number of countries, especially the UK, Australia, Japan and Chile.
It's also hoped a vaccine could be ready by the end of the year, for up to half the population.
So far, nearly 28,000 cases of swine flu have been confirmed in 74 countries around the world.
Declaring a pandemic won't make much difference to how the outbreak is handled, but could speed up the production of anti-flu medicines and get governments to consider things like travel bans to try to stop the spread of the virus.
Gregory Hartl, from the World Health Organisation, said: "A pandemic is defined by geography, not by severity.
"At this time, we have seen the huge majority of cases being self-limiting. You don't need hospitalisation."