A further 51 cases of swine flu have been confirmed in the UK, taking the total to 848.
Laboratory staff are investigating another 866 suspected cases, the Health Protection Agency has said.
The number of confirmed cases in Scotland stands at 337, with 502 in England, two in Wales and seven in Northern Ireland.
Ministers have urged the public not to panic after the World Health Organization declared a pandemic.
This followed a sharp increase in the number of cases in Australia.
UK Health Secretary Andy Burnham said: "People should not be alarmed.
"This does not fundamentally alter our approach. The disease has not so far been severe for the majority of people affected."
Maintaining good hygiene was the best line of defence, he added.
Pandemic status means the infection is spreading in at least two regions of the world.
While the virus originated in Mexico in April, it has since spread to 74 countries, infected nearly 30,000 people and caused 141 deaths.
Rising numbers of cases have been seen in the UK, Australia, Japan and Chile.
Sir Roy Anderson, an epidemiologist and the Rector of Imperial College, London, told BBC Radio 4's Today programme the UK was "well prepared" for swine flu.
He said that although the virus was more severe than seasonal influenza, it was a "mildish infection" and patients who had been hospitalised after testing positive usually had another pre-existing condition that made the infection worse.
However, with cases expected to rise in the autumn when the colder weather returns, services would come under greater pressure, he said.
"We will be stretched in terms of keeping up in terms of the number of infections."
But he added: "It is not a cause for concern, there are effective treatments."
One of the UK's worst-hit areas is Scotland, with the majority of cases affecting the Greater Glasgow and Clyde area.
The Scottish government said the rate of hospital admissions was on a par with that in the US, leading to changes to the handling of swine flu cases.
Doctors are being used to make diagnoses in some areas, rather than waiting for the results of laboratory tests, and can prescribe anti-viral drugs to those who have been in close contact with others with swine flu.
Steve Barnett, chief executive of the NHS Confederation, which represents health trusts across the UK, said the pandemic declaration reinforced the need for the thorough testing of local plans for coping with swine flu.
"We need to avoid complacency in dealing with a virus that is an unknown and seems to be spreading quickly," he said.
Mr Barnett said health chiefs had time to put safeguards in place before winter, when the spread of the H1N1 virus was expected to accelerate.
"Everything needs to be in place, from the establishment of anti-viral collection points in the community to planning for larger numbers of hospitalised children, to deal with a situation that few working in the service have ever experienced," he added.
Of the new cases in England, 10 were in the West Midlands, five in the South East, four each in the North East and London, and one each in the East and South West regions.