The World Health Organisation has declared the flu outbreaks in Mexico and the US a ‘public health event of international concern’.

WHO director general Margaret Chan urged all countries to boost their surveillance for any unusual outbreaks of influenza-like illness and severe pneumonia.

The WHO's emergency committee of experts have said more information was needed before making a decision on a possible change to the WHO's pandemic alert phase, currently three on a scale of 1 to 6.

The new flu strain, a mixture of swine, human and avian flu viruses has killed up to 68 people among 1,004 suspected cases in Mexico and infected eight in the US.

Mexico has shut schools and museums and cancelled public events.

Officials warned more cases could come to light as the flu spreads between people and infected some individuals who had no contact with one another.

Meanwhile, the Health Service Executive and the Department of Health say they are monitoring reports of the swine flu outbreak.

Public health officials met today to review the situation.

In a statement, the HSE said no cases of swine flu have been identified in Ireland or anywhere in Europe.

The HSE said there are currently no travel restrictions advised, but the situation is under active review by the WHO.

Earlier, the WHO said the virus from 12 of the Mexican patients was the same genetically as a new strain of swine flu, designated H1N1, seen in eight people in California and Texas.

Mexico's Health Minister Jose Angel Cordova encouraged people to avoid crowds and wear face masks, noting there was no guarantee that going to get a flu vaccine would help against the new strain.

He said the death rate appeared to have steadied and hospitals in the past few days had not seen the exponential rise in the number of people infected that many had feared.

Genetic analysis shows the flu strain is a never-before-seen mixture of swine, human and avian viruses.

In California, Dr Gil Chavez, director of the Centre for Infectious Diseases at the California Department of Public Health and the state's chief epidemiologist, said many more cases could come to light as patients are tested.

‘The more we look the more we are likely to find,’ he said.

In New York tests have confirmed that eight children had a type A influenza virus, likely swine flu, the city’s Health Commissioner Dr Thomas Frieden said.

Samples have been sent to the US Centres for Disease Control and Prevention for further testing to see if they are the unusual H1N1 flu strain.

About 100 students at a school in the New York City borough of Queens became sick last week, prompting the tests.

Eight people from California and Texas were infected with the H1N1 strain, but all had recovered.

Kansas state health officials have also confirmed two cases of swine flu.

In Britain, a member of cabin crew was taken to hospital with 'flu-like symptoms' today after falling ill on a British Airways flight from Mexico City to Heathrow.

A Health Protection Agency spokesman said: 'We are aware of a patient admitted to a London hospital with reported travel history to Mexico.

'As a precautionary measure the patient is being tested for a range of respiratory and other illnesses in line with UK health guidance. At present there have been no confirmed cases of human swine flu in the UK or anywhere in Europe.'