GENEVA - THE number of laboratory-confirmed swine flu cases has reached 5,251 in some 30 countries around the world, with 61 having died from the disease, the World Health Organisation said on Tuesday.

The highest number of cases has been reported in the United States with 2,600 infections, including three deaths, and Mexico with 2,059 cases, including 56 deaths, since the outbreak of new influenza A(H1N1) was reported last month, the latest data posted on the WHO website showed.

WHO has defended its decision to raise the global pandemic alarm for swine flu as Cuba, Thailand and Finland confirmed their first cases of the virus on Tuesday.

The global health body's acting Assistant Director-General Keiji Fukuda insisted the outbreak would have been more severe if the WHO had not raised its pandemic alert two weeks ago.

'If countries had not been thinking about what to do in this kind of situation, the fact is we would have had much more confusion,' Mr Fukuda said. 'In many ways, the severity would have been greater.'

The WHO raised its alert to five on a scale of six two weeks ago, signalling that a pandemic was 'imminent' after Mexico and the United States showed sustained local transmission of the influenza A(H1N1) virus.

The alert prompted countries to take specific measures, including looking at distribution of anti-viral drugs or issuing travel advice at airports.

Defending the agency, WHO's Fukuda said: 'It's often hard to see what you would have prevented by doing so much work... if things turn out that few people die, it would be the best of all possible outcomes.'

The swine flu virus was first reported in Mexico in April, but has since spread to more than 30 nations.

US health officials meanwhile reported that the 2,600 confirmed cases across the United States represented just the tip of the iceberg of actual infections.

Most of the 4,694 cases confirmed by the WHO have involved relatively mild symptoms and the virus has proved to be treatable with anti-viral drugs such as Tamiflu so far, prompting questions about whether the WHO had acted too rashly. -- AFP