, MEXICO CITY Apr 28 – The swine flu crisis deepened on Tuesday with the death toll mounting above 150 in Mexico and at least 16 countries reporting confirmed or suspected infections.
The World Health Organisation (WHO) warned meanwhile that the virus is now too "widespread to make containment a feasible" strategy.
Mexico, epicentre of the outbreak, said 152 people were now believed to have died from swine flu with more than 1,600 people suspected to be carrying the virus. Twenty of the deaths have been confirmed by laboratory tests.
The number of confirmed cases in the United States more than doubled to 44 and Britain and Spain both said they had registered patients sick with swine flu in what was the first cases in Europe.
Canada has six cases, while Israel and New Zealand confirmed their first swine flu casualties.
Suspected victims were being kept under surveillance from Australia (70 cases) to Sweden and Switzerland which had five each.
While countries tightened borders, the WHO said research since the Severe Acute Respiratory Syndrome (SARS) outbreak in 2003 in Asia had shown that border controls were of little use in halting the spread of such a virus.
"Border controls do not work. Screening doesn’t work," WHO spokesman Gregory Hartl said in Geneva.
"If a person has been exposed or infected… the person might not be symptomatic at the airport," he said. "We learn as we go on. SARS was a huge learning experience for all of us."
WHO assistant general secretary Keiji Fukuda warned on Monday that the virus would be impossible to contain.
"I think that in this age of global travel where people move around in airplanes so quickly, there is no region to which this virus could not spread," said Fukuda.
Fukuda said WHO experts decided at a meeting on Monday that the virus is too "widespread to make containment a feasible" strategy and that the UN health agency did not recommend closing borders or restricting travel.
British Prime Minister Gordon Brown ordered a meeting of his government’s top emergency preparations committee to discuss the swine flu crisis.
"Swine flu is an international problem now, it’s crossed two continents, it’s got to be dealt with by international agreements," said Brown.
In Asia, South Korea said it was investigating one suspected infection, while at least three people have been confirmed as New Zealand’s first swine flu cases but 10 are assumed to have caught the virus, Health Minister Tony Ryall said.
WHO officials in China said they were investigating several people with suspicious symptoms, but played down the chances that any were infected.
Japan said it would temporarily tighten visa restrictions for Mexican nationals as part of efforts to stop the virus entering the country.
It also booked 500 hotel rooms near Tokyo’s Narita airport in case infected travellers need to be quarantined, Jiji Press news agency reported.
An Israeli recently returned from Mexico has been confirmed to have contracted the first case of swine flu in the Middle East, Israeli military radio reported.
Dmitry Lvov, head of the Russian Academy of Sciences’ Institute of Virology, said the risk of a worldwide pandemic was "very high. It could reach Russia in a week."
"It all depends on whether the new countries affected can contain its development," said Lvov.
Australian authorities said on Tuesday they were investigating 70 possible cases of swine flu and cautioned against travel to Mexico.
Prime Minister Kevin Rudd vowed to devote "all necessary resources" to the evolving flu threat, as possible cases of the disease more than doubled, covering all but one of the country’s states and territories.
UN chief Ban Ki-moon warned the new multi-strain virus , which is believed to be a mix of a human flu virus and an avian flu that first came from swine, risked triggering a global pandemic.
"We are concerned that this virus could cause a new influenza pandemic. It could be mild in its effect or potentially be severe," Ban told reporters.
"We don’t know yet which way it will go but we are concerned that in Mexico most of those who died were young and healthy adults."
Fears the virus could further hit the struggling global economy spooked investors, with stocks across Europe’s leading markets sliding in opening trade following sharp losses in Asia.
Oil prices suffered new falls amid worries that the outbreak would hurt air travel and hit demand.