Britain has announced nine new swine flu cases, including seven people who had not travelled to Mexico.
Health officials say the total number of infections is now 27.
They say seven of those diagnosed were children, including five from a school in Dulwich, south London, which already had one confirmed case: a pupil who recently returned from the United States.
They say all five caught the virus through person-to-person contact.
Five schools have been closed in Britain, including one in north London and two in western England.
Restaurants and cafes in Mexico City to reopen
Restaurants and cafes in Mexico City are to reopen on Wednesday after a fall was reported in new cases of the swine flu virus.
The mayor's office said libraries, museums and churches are to follow suit a day later but cinemas, theatres and bars are to remain closed.
Government officials are meeting to discuss when schools and businesses across the country can resume work.
Health Minister Jose Angel Cordova said on Monday that swine flu has been confirmed as the cause of 26 deaths in Mexico and 701 people have been infected.
Earlier, he said the epidemic was "in its phase of decline", having peaked between 23 - 28 April.
A total of 1025 cases of the virus have now been reported in 20 countries.
The United Nations says it has seen no evidence of a spread of the disease at a community level in Europe and Asia - a development that would trigger the highest level of pandemic alert.