More than 800 people have been confirmed with swine flu in the UK
People in the UK have been urged to remain calm after the World Health Organization announced swine flu had reached the pandemic stage.
Government officials said the move did not "fundamentally alter" the approach being taken which is based on containing local outbreaks.
More than 800 cases have been confirmed in the UK.
But as yet the virus has not spread as rapidly as it has in other countries such as the US, Mexico and Australia.
Andy Burnham, the Health Secretary in England who this week chaired the UK's emergency planning committee Cobra, said the WHO move had been expected.
"It does not fundamentally alter our approach in the UK so people should not be alarmed.
"We continue to be on top of the situation.
"We have based our actions so far on a very strong and well rehearsed flu plan."
He said the best advice was for people to follow good hand hygiene to stop the spread of the disease.
Chief Medical Officer Sir Liam Donaldson agreed.
He said health protection officials were still operating a containment approach.
This involves isolating people with the flu, giving them anti-virals to lessen the symptoms and shorten the length of the illness as well as tracing people they have come into contact with and giving them drugs in an attempt to stop the disease developing.
Sir Liam said: "At the moment if we continue to get a steady number of cases we can continue this for quite a bit longer."
He added a surge in the number of cases could probably be expected in the autumn, but the key would be if the virus mutated to become more virulent.
But he added: "That is still the least likely scenario."
Under the flu contingency plans, the government can restrict movement and public gathering, such as concerts.
If there was a significant rise in the number of cases ministers can also stop giving anti-virals preventatively and instead just give it to people who develop the illness.
However, the move to a pandemic phase may make it slightly more difficult to get a supply of vaccines.
The UK government has a pre-pandemic contract for vaccines, but the move to pandemic status triggers deals many other countries had with suppliers.
Sir Liam said: "It does not make it as easy, but we still expect to get vaccines in the autumn."