The WHO has arrived at its prognosis by studying how the illness has been progressing in the southern hemisphere - in Southeast Asia and Australia, for example - where countries are currently experiencing winter and their annual influenza season.

The agency's Western Pacific director, Shin Young-soo, said on a visit to China on Friday that there would soon be a further global spread of the virus. He predicted that is was likely that most countries would see swine flu cases "double every three to four days for several months" until a peak transmission period is reached.

Earlier this year, the WHO declared the swine flu strain, (A)H1N1, a pandemic. Through last week, the illness had killed almost 1,800 people worldwide and spread to 180 countries with more than 177,000 confirmed cases.

Study says 'vaccinate children'

New research has suggested that the best way to protect against the spread of the virus was to vaccinate school-age children and their parents. Unlike most strains of flu, which are usually most dangerous to older adults, (A)H1N1 targets younger people, according to a report published in the journal Science on Thursday.

The report recommends making children the top priority because they are the influenza's prime transmitters and their parents are the virus' bridge to the rest of the community. Inoculating spreaders, the report contends, would create a 'cocoon' around the people most at risk.

Many countries, including Germany, have begun stockpiling millions of doses of vaccine in anticipation of a second, and more significant, outbreak of swine flu when the northern hemisphere's winter begins a few months from now.

gb/AP/Reuters
Editor: Nancy Isenson