The World Health Organisation (WHO) has today declared the AH1N1 virus (swine flu) the first pandemic of the 21st century.  The virus, which was first detected at the end of April in Mexico, has affected some 28,000 people in 74 countries across the globe, proving fatal in 141 cases.

The director general of the WHO, Margaret Chan, has nevertheless made it clear that the alert has been raised to the highest level worldwide (level 6) not because a sudden increase in cases is expected or because the virus iss set to suddenly cause more fatalities. 'The word pandemia relates to the spread of the virus,' she explained.

Although Chan maintained that it was 'a moderate pandemic' on a global scale, she stressed that each government would have to assess its country's individual situation and act accordingly, taking into account the degree of vulnerability of its citizens in general.

Chan called for calm, reiterating that the vast majority of cases had been very mild (only 2% have been classified as serious) , but also warned that this was not the moment to let down the collective guard. So far the virus has mainly affected young people (under 25s).

With regard to Mexico, where the pandemic began, a second wave of cases of the virus could well be on the cards, she warned, even though the spread of it appears to be under control at the moment.

The head of the WHO added that with 'bird flu' still considered to be a level 3 risk, this was an historical first, with two viral pandemics in the world at the same time.