Four more people were confirmed with the swine flu virus today, taking the total number in the UK to 137, health officials said.
The four new cases, which included three children and an adult, were from London, the South East and the West Midlands, the Health Protection Agency said.
Three of the patients were linked to previously confirmed cases while one had recently returned from abroad.
The total number of cases in England has now reached 123, with 13 in Scotland and one in Northern Ireland.
A spokesman for the Department of Health said: "The localised cases of swine flu found in the UK have so far been mild, and our strategy of containing the spread with anti-virals appears to have been effective in reducing symptoms and preventing further spread of infection.
"But we must not be complacent - it is right to prepare for the possibility of a global pandemic. The UK's arrangements are continuing to ensure that we are well-placed to deal with this new infection."