Swine flu hit Europe with the first confirmed cases in Britain and Spain on Monday as governments and travel companies urged travellers to avoid Mexico where the virus has likely killed 149 people.
The European Union called for urgent talks to confront the threat, and advised against non-essential travel to parts of the United States and Mexico where infections of the new strain of the H1N1 virus had broken out.
World health officials have stepped up the battle against the virus as Mexico upped the probable death toll and after the United States declared a public health emergency.
The World Health Organisation late Monday raised its flu pandemic alert level from three to four, signalling a significant increase in risk of a pandemic, but said travel restrictions were not justified.
Tests of suspected cases were being carried out across Europe, including six in Belgium, five each in Denmark, Sweden and Switzerland, three each in Ireland and the Czech Republic and one in France. Several other cases tested negative.
Spain's health ministry said tests on a 23-year-old man who returned from Mexico last week confirmed he had contracted swine flu, and a further 26 cases were suspected there.
Hours later, two people hospitalised in Scotland after travelling to Mexico were confirmed as the first cases in Britain.
"I can confirm that tests have demonstrated conclusively that the two Scottish cases of swine flu are positive," said Scottish Health Minister Nicola Sturgeon, adding the pair -- reportedly a couple -- were "recovering well."
Seven other people who came into contact with them, among 22 tested, have developed mild symptoms of the flu and were being treated at home, she said, adding: "I would reiterate that the threat to the public remains low."
The health minister for the government in London, Alan Johnson, said earlier that "enhanced" health checks were being implemented at entry points across the British Isles to identify passengers arriving with symptoms of the illness.
There was confusion over travel advice, as the EU health commissioner advised against non-essential travel to areas of the US and Mexico but the WHO said it had made no such recommendations.
People "should avoid travelling to Mexico or the USA unless it's very urgent for them", said EU health chief Androulla Vassiliou, saying this would "minimise the personal risk and reduce the potential risk to spread the infection."
She later told the BBC: "I meant advice, not a ban, to Mexico City especially and those states in the US where we have many outbreaks."
Her spokeswoman also underlined she was not advising against travel to Spain.
The EU advice drew a sharp retort in the United States, where 40 cases of swine flu have now been confirmed, and fears for cutbacks in travel battered airline shares in markets Monday.
A German tour operator cancelled trips to Mexico, Russia began airport checks and Poland tightened border controls.
The Czech Republic and France's health minister also joined in advising against non-essential travel to outbreak areas in Mexico.
Ukraine has banned the import of pork products from Mexico, the US, Canada and New Zealand, where 10 suspect cases have also been identified.
European Commission chief Jose Manuel Barroso said European authorities would remain vigilant.
"We will continue to assess the information we are getting from the experts, evaluate the potential danger and decide together with member states on the measures to take," he said.
(c) 2009 AFP