Swine flu is beginning to spread from travellers to residents of the UK, according to the Health Protection Agency.
A further 10 cases were announced yesterday, bringing the total number in the UK to 65, said the HPA.
In the East of England, swine flu infection has been confirmed in an adult and a child returning to the country and an adult who is a close contact of a previously confirmed case.
The cause of infection of another adult remains under investigation.
In London, two cases, an adult and a child, are returning travellers and one adult is a returning traveller.
Some of the cases may have now recovered and be symptom-free because of the time taken to take swabs, test and confirm results.
According to the World Health Organisation, there have been 4,694 cases of H1N1 influenza A in 30 countries.