Cases of swine flu, which has killed people in Mexico, have been confirmed around the world. With experts scrambling to develop a vaccine, there is concern at the potential for a pandemic affecting millions of people. What is swine flu? Swine flu is a respiratory disease, caused by influenza type A which infects pigs.
There are many types, and the infection is constantly changing.
Until now it has not normally infected humans, but the latest form clearly does, and can be spread from person to person - probably through coughing and sneezing.
How dangerous is it? Symptoms of swine flu in humans appear to be similar to those produced by standard, seasonal flu.
These include fever, cough, sore throat, body aches, chills and fatigue.
It is worth remembering that seasonal flu often poses a serious threat to public health: each year it kills 250,000 - 500,000 around the world.
So far, most cases of swine flu around the world appear to be mild, albeit with diarrhoea more common than it is with seasonal flu.
But lives have been lost in Mexico, and a single death - of a Mexican child - has been confirmed in the US.
Is Mexico different? The death toll in Mexico - where the virus at present seems to producing much more severe symptoms - suggests there may be unusual factors coming into play there.
Some experts have suggested the possibility that other, unrelated viruses may also be circulating in Mexico, making symptoms worse.
This would be unlikely to come into play in the rest of the world.
Alternatively, people infected in Mexico may have sought treatment at a much later stage than those in other countries.
It may also be the case that the form of the virus circulating in Mexico is subtly different to that elsewhere - although that will only be confirmed by laboratory analysis.
The Mexican authorities have downgraded the official death toll from the virus, ordering a new round of more stringent tests
Can the virus be contained? The virus appears already to have started to spread around the world, and most experts believe that, in the era of readily available air travel, containment will be extremely difficult.
The World Health Organization says that restricting flights will have little effect. It argues that screening of passengers is also unlikely to have much impact, as symptoms may not be apparent in many infected people.
Can it be treated? The US authorities say that two drugs commonly used to treat flu, Tamiflu and Relenza, seem to be effective at treating cases that have occurred there so far. However, the drugs must be administered at an early stage to be effective.
Use of these drugs may also make it less likely that infected people will pass the virus on to others.
The UK Government already has a stockpile of Tamiflu, ordered as a precaution against a pandemic.
However, there is concern that if too many people start taking anti-virals as a precaution, it could raise the risk of the virus developing resistance, reducing the drugs' effectiveness.
Subject: Swine Flu 
Fri May 01, 2009 7:26 pm
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