British health officials have confirmed five new cases of swine flu, bringing the national total to 39.
The cases are in four children and an adult who are all associated with a school in London.
The Department of Health said Friday that the school had been closed as a precaution and staff and students given antiviral drugs.
On Thursday Health Secretary Alan Johnson said authorities expected more British cases of the disease, but there was not yet any evidence of sustained person-to-person transmission. No one in Britain has died of the flu.
Most of the British cases are in people who recently traveled to Mexico, the epicenter of the swine flu outbreak.