The first genetic code of swine flu from European samples has been unravelled by UK researchers.
The Health Protection Agency has also announced it has now shared isolates of the UK virus with scientists working on a vaccine against the strain.
It will enable researchers to compare the virus affecting humans in Europe with that in Mexico and the US and look at the immune reaction it causes.
Health secretary Alan Johnson said the work was a "significant step".
Researchers at the US Centers for Disease Control and Prevention had already made genetic information on the swine flu virus publicly available to scientists around the world.
But a team at the National Institute for Biological Standards and Control (NIBSC) have been specifically working on getting the full genetic fingerprint of the virus that has infected Europeans.
They will also share the information globally which will help scientists better understand how the virus behaves as it infects people.
And because viruses have the potential to evolve and change their behaviour as they spread, researchers are also keen to keep an eye on any changes that might occur as more people become infected.
