Health Protection Agency (HPA) researchers have found that the vast majority of people in the UK hit by norovirus this season have been infected with a new strain called Sydney 2012. The strain takes its name from the Australian city where it was first identified.
The HPA said the new strain was not more harmful than others and said the same precautions, including hand-washing, should be taken.
This season's norovirus outbreak has hit 1.2m people and led to 673 reported hospital outbreaks, including 33 over the Christmas and New Year period.
Dr David Brown, director of the HPA's Virology Reference Department, said: 'Noroviruses mutate rapidly and new strains are constantly emerging. At the start of the season it is normal for outbreaks to be caused by a range of different strains. However as the season progresses particular strains are more successful and become dominant.'
He added: 'The emergence of a new strain does not mean that it causes more serious illness and managing outbreaks and those with the illness remains the same.'
An international team of researchers behind the paper said it remained unclear whether this new strain had caused the larger-than-usual global outbreaks of norovirus. They said more data was needed to prove an association.