The World Health Organisation has raised its Mexican flu pandemic alert to level 6, officially declaring the first pandemic of the 21st century.

A pandemic means an epidemic has spread across continents or even across the world. This is the first time in 41 years that a pandemic has been declared.

In 1968, about a million people were killed in the Hongkong flu pandemic, but the Mexican flu is considered a much less dangerous virus. The WHO says it will not be necessary to close borders or put limitations on the free movement of goods and people, but the organisation did warn that a second wave of infections may be imminent. The new flu virus, named A(H1N1), has spread to 74 countries in America, Europe and Asia since April. An estimated 28,000 people have become infected, of which 141 have died so far.

The WHO alert level 6 means all associated countries must make preparations for a more intensive fight against the disease. The Dutch authorities say alert level 6 has no direct consequences for the Netherlands. In the past week, the number of Dutch people infected has risen to 35. Most of them caught the virus abroad, nine were infected in the Netherlands.

Photo by Nwara - bye bye (Flickr)