Two patients in a Scotland who returned last week from a visit to Mexico were today confirmed as suffering from swine flu.
The news came after Britons were urged to postpone non-essential travel to the United States or Mexico as senior officials held emergency talks over the deadly outbreak of swine flu.
The European Union's health commissioner Andorra Vassiliou met EU foreign ministers on the subject and advised people to reassess their travel plans.
"They should avoid travelling to Mexico or the United States of America unless it is very urgent for them," she said.
In the UK, the two cases were confirmed this evening. The two people remain in hospital in Scotland and Scotland's Health Secretary Nicola Sturgeon said their condition gave no cause for concern and both patients are "recovering well".
The pair, who arrived back in Scotland from Mexico last Tuesday, are being treated in Monklands Hospital in Airdrie, Lanarkshire
Ms Sturgeon said that seven people among the 22 who had been in contact with the two infected individuals have developed "mild symptoms" which have not been comfirmed as swine flu and are being "appropriately cared for".
She added they were receiving drugs at home, not in hospital.
Ms Sturgeon added: "I would reiterate that the threat to the public remains low and that the precautionary actions we have taken over the last two days have been important in allowing us to respond appropriately and give us the best prospect of disrupting the spread of the virus.
"However, this is a developing situation which we continue to monitor very closely, in conjunction with our colleagues in other parts of the UK and the World Health Organisation."
Officials in Spain had earlier confirmed Europe's first case of swine flu. Spain's health minister Trinidad Jimenez said the case involved a man who had recently been in Mexico and said he was responding well to treatment and was not in a serious condition.
In the US, New York City has 45 confirmed or likely cases of swine flu and that number is likely to rise as testing of more than 100 sick students continued, Mayor Michael Bloomberg said today. The outbreak of swine flu appeared to be contained to one high school in the borough of Queens, he said. Meanwhile the government is recommending that non-essential travel to Mexico is avoided.
NHS North West, a regional strategic health authority, announced late this afternoon that tests had cleared a Canadian woman was being treated for suspected swine flu in Sale, Greater Manchester.
The Health Secretary Alan Johnson earlier told the Commons that in the UK 25 cases of possible swine flu had been reported of which three were currently undergoing further specialist tests. Mr Johnson said that eight cases had proved negative while the remaining 14 were undergoing initial investigation but were sufficiently well to be managed in the community.
He said that if the virus started spreading widely in the UK the Government proposed to use its stockpile of anti-viral drugs to treat patients showing symptoms of the disease. The Government was working with primary health care trusts to ensure that arrangements for the distribution of anti-virals were in place should this become necessary.
Earlier, a British businessman who had been told to stay away from other people after he also returned from Mexico with flu-like symptoms was given the all-clear. Chris Clarke, from Stanwick, Northamptonshire, said it was "very good news".
"I think it isn't unusual to feel slightly run-down after a long-haul flight but there was always an outside possibility that it was something more sinister than common or garden flu," he told BBC Breakfast.
"I was reasonably relaxed because, statistically, the chances of having picked up anything in Mexico were relatively low but of course I have two young children and it is concerning to think that you might have brought something untoward back into the household."
Anyone who feels unwell and suspects they have flu is advised to visit the NHS Direct website at www.nhsdirect.nhs.uk .
Under the civil contingencies committee system - known as Cobra - cross-departmental representatives, including senior officials but no ministers, met this morning to plan how to deal with any outbreak of the H1N1 strain of the virus.
Public health experts from all EU countries were also summoned to Brussels for urgent talks on the swine flu outbreak this afternoon after more than 100 people were killed by the virus in Mexico.
The meeting is the first in a series being convened by the current Czech EU presidency in the run-up to an emergency meeting of EU health ministers, probably on Thursday.
At Gatwick airport in west Sussex, Britons arriving back from Mexico were questioned by a doctor on board about possible flu symptoms before leaving the aircraft.
Trevor Cox, 65, from Dover, Kent, was among passengers arriving on the Thomson Airways 358 flight from Cancun following a two-week sunshine break with his wife Kathy.
He said: "I thought we might have problems this end with a screening process, but a doctor just came on board and asked if anyone was feeling ill or experiencing diarrhoea, then basically left it up to passengers. I think one or two people came forward.
Health Secretary Alan Johnson, who is expected to make a statement on the issue later today, said yesterday he had no doubt that there would be more cases of travellers coming into the UK with flu-like symptoms and promised that they would be examined "very, very quickly" by the NHS.
The NHS has a stockpile of more than £500m-worth of the Tamiflu anti-viral drug which has proved effective on patients in Mexico, and scientists are working on developing a vaccine against the new strain, said Mr Johnson.
The Department of Health said it has stepped up surveillance arrangements, adding that the UK has enough antiviral stocks to provide treatment for 50 per cent of the population if they become ill.
"We put plans in place earlier this year to increase supplies of flu drugs, making the UK one of the most prepared countries in the world," a spokesman said.
World Health Organisation (WHO) director-general Margaret Chan said the outbreak, caused when the H1N1 strain associated with pigs crossed over to the human population, constituted a "public health emergency of international concern" and had "pandemic potential".
The WHO plans to hold a press conference on the issue in Cairo, Egypt, tomorrow.
To prevent the spread of illness, the Health Protection Agency advised people to cover their nose and mouth when coughing or sneezing, to throw away dirty tissues promptly and carefully, and to wash hands and surfaces which are regularly touched.
Northern Ireland health minister Michael McGimpsey briefed the Northern Ireland Assembly.
"We don't have vaccines - it will take about six months, three to six months for that to be produced.
"What we are using are anti-virals and those are in fact the Tamiflu anti-virals which is what we are using for those who contract the flu," he said.