Three new cases of swine flu have been confirmed, taking the UK total to 112, health officials said.
The Department of Health said the new cases were all children from the West Midlands recently returned from trips abroad.
A Department of Health spokesman 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."
The latest World Health Organisation (WHO) figures showed 11,034 people in 41 countries were infected with swine flu, with 85 deaths, mostly in Mexico.
The Health Protection Agency (HPA) has issued health advice for people travelling abroad over half term.
Travellers are advised to check the Foreign Office website for information about their destination and follow basic hygiene rules when they are there.
A spokesman said anyone returning from a country affected by the outbreak who develops flu-like symptoms within a week of their return should stay at home and contact their GP or NHS Direct on 0845 4647.