Swine flu declared a pandemic

The World Health Organization has declared that the spread of swine flu is now a global pandemic, the first flu pandemic for 41 years.

The WHO's director general, Margaret Chan, raised its pandemic alert to the highest level, phase six, on 11 June.

What is swine flu?

Swine flu is a new strain of the H1N1 influenza virus, which contains genes from viruses found in pigs, birds and humans. It was first identified in Mexico and the United States in April.

It has since spread to more than 70 countries, with around 30,000 confirmed cases and more than 140 deaths.

Moderate severity

Dr Chan said the declaration reflected the spread of the virus, not its severity. So far, most people who catch it have mild symptoms and recover without treatment. But some people, including pregnant women and those with existing health conditions, may be at greater risk.

Unusually for flu, the virus seems to affect younger people more than the elderly.

The UK

There have been hundreds of confirmed cases in the UK, with the largest outbreaks in Scotland and in the Midlands, including a number of schools in Birmingham, some of which have closed temporarily.

The government has stockpiled antiviral drugs, including Tamiflu, and has ordered vaccines. The Health Secretary, Andy Burnham, said the UK was one of the best prepared countries in the world.

Vaccines

Drug companies are developing a vaccine against the new strain, but it is not expected to be available for several months.

Advice

People are being advised to follow the "catch it, bin it, kill it" advice: to use tissues when they cough or sneeze, throw them away and wash their hands. Those with symptoms are advised to stay at home.

Previous pandemics

The last flu pandemic, known as Hong Kong flu, was in 1968. The most deadly, the Spanish flu of 1918, killed tens of millions of people around the world.

Experts say the declaration does not mean people should panic, but that countries should prepare for the virus to spread further, particularly when the flu season begins in the northern hemisphere this autumn.