Despite the World Health Organization (WHO) raising the alert level for swine flu to phase five of six, the government has insisted it remains "business as usual".
The upgrade means the WHO believes swine flu is spreading from human to human in at least two countries and a global outbreak is imminent.
Efforts to produce a vaccine will be heightened after three more Britons were confirmed as having the illness, including a schoolgirl from Devon.
The government's chief medical adviser, Professor Sir Liam Donaldson, warned that the new alert level means the WHO considers a global pandemic to be imminent.
He added that countries would now ramp up preparations, with Britain already taking action.
Vaccine stockpiles are being increased from levels which would cover 33 million people to 50 million, and surgical masks will be provided for frontline NHS staff.
Airlines will have to keep a record of passengers for a period extending the usual 24 hours, and the Health Protection Agency will monitor travellers coming in from affected areas.
A total of 76 people have been screened for the virus in the UK, with 32 possible cases in Scotland and 20 in Wales.
Copyright © Press Association 2009
Is primary care prepared for a swine flu outbreak? Your comments (terms and conditions apply):
"We have been offering up plans for about four years on this, so we ought to be! Plans have to be flexible however, as we do not know what will actually happen to staff, supplies and other factors beyond our control. I think the best advice I've heard is 'don't panic'" – Name and address withheld