In depth: Influenza pandemics
Up to 50 million died in the Spanish flu pandemic
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Friday, 12, Jun 2009 09:00
As the World Health Organisation prepares to announce that swine flu has become a global pandemic, inthenews.co.uk looks back on the influenza pandemics of recent history.
An influenza pandemic is an epidemic of a virus on a worldwide scale that infects a large proportion of the population.
There have been more than 27,000 swine flu cases and 141 since the virus first emerged in Mexico in late April.
No one has died outside of the Americas, but in recent weeks there have been hundreds of new cases in Japan, Australia and Europe.
In the past century that have been three influenza pandemics, all of which were caused by a new strain of the virus being transmitted to humans from another animal species.
The first and greatest of the 20th century was the outbreak of Spanish flu, which began in 1918 and has been compared to a modern-day version of the Black Death.
Just months after peace was reached in Europe, a new and deadly threat rampaged across the globe, killing more than 50 million people, far more than died during the first world war.
Up to one fifth of people infected with the virus died from it, resulting in a category five pandemic rating.
The pandemic was also notable for the high proportion of healthy young adults affected by the virus, which usually has the greatest effect on the very young and very old.
In 1957 the two-year Asian flu pandemic began when a wild duck virus combined with a human strain.
The category two pandemic spread across most of south-east Asia and later the United States, where 70,000 people died.
Another category two pandemic began in 1968 and lasted until the following year in the shape of Hong Kong flu.
More than 500,000 people were infected, although the death-rate was considerably lower than the two pandemics that preceded it.
Much more recently, dire warnings were sounded about a potential pandemic that could take an even greater toll.
Avian influenza, otherwise known as bird flu, entered the public mindset when pre-pandemic influenza vaccines went into production after warnings were first issued in 2003 over the potential person-to-person transmission of a highly pathogenic strain of the virus, following the deaths of six people six years earlier.
The World Health Organisation has called an emergency meeting at its Geneva headquarters to consider whether the H1N1 virus is a global pandemic.
Dr Margaret Chan, WHO general secretary, said on Wednesday after holding talks with officials from eight of the worst-affected countries: "Once I get indisputable evidence I will make the announcement."