By News Editor Declan Wilkes

Passengers arriving at Heathrow airport are being screened for symptoms of the deadly swine flu virus.

The capital's hospitals are also on alert, preparing isolation rooms for patients suspected of having the illness - the potential for infection is high given that the flu can be spread from human to human through coughing and sneezing rather through human animal contact.

At the UK's busiest airport, passengers from Mexico are being held on planes for 45 minutes whilst being screened by mask wearing health officials.

Passengers trapped on the runway are being asked if they have any symptoms - tests on two people in Scotland suffering from "flu-like symptoms" after returning from Mexico are ongoing.

There were fears that people could have brought the disease into the UK and had not yet developed symptoms.

Monitor for seven days

The Health Protection Agency and the British Airport Authority are advising passengers returning from a visit to an affected area to monitor their health closely for seven days.

If during this period you develop a feverish illness accompanied by one or more of a cough, sore throat, headache or muscle aches, you should stay at home and contact your GP by phone or seek advice from NHS Direct (0845 4647).

Virus in Europe

There are fears the outbreak could turn into a worldwide pandemic that could kill 120 million.

Governments across the world are implementing action plans - at "ground zero" in Mexico, 103 people have already died. 40 cases have been confirmed in the Southern United States.

The virus has reached Europe; a case confirmed in Spain today, doctors in France, Israel and New Zealand are also keeping an eye on suspected infections.

UK cases "expected"

Head of the Health Protection Agency Justin McCracken said we are expecting cases "given the way this has spread across America."

But he added that the UK was one of the best equipped countries in the world to combat the disease after stockpiling £500m of anti-viral drugs - enough for half the population, saying:

"I don't think at this stage there is any need to declare an emergency."

No travel restrictions

A spokesman for the industry trade body, the International Air Transport Association, said that it was taking advice from the World Health Organisation, adding:

"We are working with both bodies and at this point we have been told that there is no need to impose restrictions on travel."

If the crisis escalates, airlines are ready to implement the guidelines that were last used during the SARS outbreak in 2003.

This would include pre-screening of passengers who displayed any symptoms of the disease at airports in any of the affected countries.

Over 300,000 Brits visit Mexico - seven airlines fly Heathrow route

In 2008, 315,568 British nationals visited Mexico.

Seven airlines offer direct or indirect flights from Heathrow to Mexico City: British Airways, United, KLM, Iberia, AeroMexico, American and Mexicana.

A British Airways spokesman said that it would continue to operate its daily service to Mexico City.

However crew on the route had been told they should contact their GP immediately if they developed any flu symptoms.

Cobra meeting - European Commission  - WHO

An emergency meeting of Cobra - which is when government departments meet in response to national crises - was convened today and Health Minister Alan Johnson is expected to make a statement to the House of Commons.

The Prime Minister is currently in Pakistan.

Johnson said that any travellers coming into the UK with flu-like symptoms would be seen "very, very quickly" by the NHS.

The European Commission also called for an urgent meeting of health ministers while the World Health Organisation convene tomorrow to discuss raising the pandemic threat level, currently at three, six is the most serious.

Billions have been wiped off the value of airlines, travel companies and hotel groups as the stock markets responded to the fears, with shares in British Airways down 12 per cent.