Three more people in the UK have been diagnosed with swine flu, the Department of Health said today.
A total of eight people have now been confirmed with the disease.
A DH spokesman said: "There have been three more confirmed cases of swine flu in the UK - two in London and one in the North East.
"There are now eight confirmed cases in the UK - six in England, and two in Scotland.
"The preparations we have in place and are continuing to make will help to ensure we respond well in the event of a pandemic."
The Health Protection Agency said 230 possible cases were under investigation.
Of the three new cases, one is understood to involve a patient who lives with two students from Newcastle University.
An HPA spokesman said: "All have mild symptoms and are responding to treatment at home.
"The Health Protection Agency is working to ensure that any close contacts of the three patients are offered anti-virals as a precautionary measure.
"At this stage close contacts who should be offered anti-virals as a precautionary measure are those individuals who have been exposed to a probable or confirmed case within the previous seven days for longer than one hour and within a distance of one metre or less.
"All cases up to now have been associated with travel to Mexico."
Yesterday Prime Minister Gordon Brown confirmed that a 12-year-old schoolgirl, from Torbay in Devon, a 41-year-old woman, from Redditch, Worcestershire, and a 22-year-old man, from Barnet, north west London, all contracted the disease after visiting Mexico.
And today Britain's first confirmed victims, Iain and Dawn Askham, of Polmont, near Falkirk, were released from hospital after falling ill on their return from honeymoon.
A public health campaign has also begun, with newspapers, television and radio carrying adverts warning people about the disease and how to help prevent it spreading.
The public is being urged to use tissues, throw them away afterwards, and regularly wash their hands.
Earlier, Mr Brown said: "I do want to reassure the British people that we are taking all the precautions that are necessary.
"We have been prepared for a scenario such as this for many years.
"I have absolutely no doubt there will be more cases. We have the supplies in place and are ready to respond to the needs of the British people."
Professor Sir Liam Donaldson, the Government's Chief Medical Officer, told BBC Breakfast: "What we will see is many, many more cases, but on the whole most people make a good recovery from flu.
"I'm concerned, but I'm not alarmed. We have a very strong plan in place."
The World Health Organisation (WHO) has raised the alert level to phase five of six, meaning a global outbreak is imminent.
Holland and Switzerland both confirmed their first cases of swine flu today, bringing the total number of countries affected around the world to 11.
There have been 168 deaths in Mexico with eight confirmed as definitely due to the virus.
The other countries affected are the US, Canada, New Zealand, Germany, Spain, Israel and Austria.