A DEADLY strain of flu that combines elements of swine, avian and human viruses could spread around the world after emerging simultaneously in Mexico and the United States, experts warned yesterday.

Margaret Chan, director-general of the World Health Organisation, declared the disease a “public health event of international concern” after an emergency meeting in Geneva last night. She said the disease had “pandemic potential” and urged all countries to keep a close watch for outbreaks of influenza-like illness.

A British Airways cabin crew member was taken to hospital with flu-like symptoms yesterday afternoon after falling ill on a flight from Mexico City to Heathrow. The Health Protection Agency said it was keeping a close eye on the situation.

Britons are not being advised to avoid travelling to affected areas, although anyone visiting those destinations or who has recently returned should consult a doctor if they experience flu-like symptoms.

In Mexico up to 81 people have died from pneumonia caused by the swine-flu virus and more than 1,000 suspected cases have been reported.

Mexican soldiers distributed surgical masks and the authorities warned people to avoid shaking hands and kissing.

The mayor of Mexico City cancelled all public events, and schools, museums, cinemas and libraries were closed. Health workers were posted at airports and at stations to keep anyone showing symptoms off public transport.

US scientists said Mexicans had been dying for weeks before the virus - an animal strain of H1N1, the virus that killed 50m in the Spanish flu pandemic of 1918 - was detected. Controlling people’s movements might not now keep it from spreading, they said.

“It is clear that this is widespread,” said Dr Anne Schuchat of the US Centers for Disease Control and Prevention.

Swine flu has also been identified in isolated outbreaks across America. There have been seven cases in California, three in Texas and two in Kansas.

Eight New York schoolchildren have been infected with a flu virus that officials think is likely to be identical. Most of the American patients, except those in New York, have already recovered.

The British Airways crew member was taken to Northwick Park hospital in Harrow, northwest London, after flight BA242 landed at 2pm.

“The patient was admitted directly to a side room and the hospital is scrupulously following infection control procedures to ensure there is no risk to any other individual in the hospital,” the hospital said.

The Port Health Authority, the agency responsible for disease containment at the UK’s borders, is asking crew on flights into Britain from Mexico to report any passengers suffering from coughs and sneezes to medics.

Danger of hybrid viruses

People who are around pigs are most likely to be infected by the H1N1 virus, but the virus can spread from person to person.

Avian flu, which has killed 250 people since 2003 and sparked the last pandemic threat, is caused by influenza viruses adapted to infect birds. Swine flu is caused by viruses adapted to pigs. Big problems arise when human and animal flu viruses mix and mutate into new organisms that can spread through the population.

The fact that most of the Mexican dead were aged between 25 and 45 rather than being elderly or very young is seen as a particularly worrying sign. The first victims of the Spanish flu pandemic of 1918 were also healthy young adults.

The symptoms of swine flu in people include fever, fatigue, lack of appetite, coughing and sore throat.

Michael Osterholm, a pandemic flu expert at the University of Minnesota, said new cases were probably already incubating around the world.

Tamiflu, an antiviral drug used against bird flu, is said to be effective against the new strain.

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