Some specialists say there is no question that a swine flu vaccine must be produced but WHO needs to discuss the issue with its members.
As of yesterday, the swine flu virus, which WHO calls the A (H1N1) virus, has sickened at least 8,480 people in 40 countries, killing 75 of them, mostly in Mexico.
Japan's health ministry confirmed dozens of new cases of swine flu in waves of announcements yesterday, prompting the government to shut down schools and cancel public events. By late yesterday, Japan's tally rose from five confirmed cases to 78, many of them high school students who had not traveled overseas.
Most new cases involved students in the western prefectures of Hyogo and Osaka. Health officials said they were recovering in local hospitals or at home.
Customer service workers at stores, restaurants, and train stations in those two regions immediately began wearing masks as a precaution.
"We have not determined how the virus spread in the region, and we are doing our best to track down the route of the infections and contain them," Chief Cabinet Secretary Takeo Kawamura said.
Japan had established strict quarantines at airports, but decided on Saturday to focus on containing the domestic outbreak.
WHO spokesman Gregory Hartl said in-country transmission rates were a key factor in whether the global body decides to increase its pandemic alert level. Right now, the world is at phase 5 - out of a possible 6 - meaning that a global outbreak is "imminent."
"We already know about the UK and Spain, that they have a relatively high number of cases compared to other European countries, so by simple virtue of the fact that they have more cases they need to be kept an eye on," Hartl said in an interview with AP Television News.
"There seems to have been activity in the last few days in Japan so we need to watch that too," he said.
Spain and Britain have had the highest numbers of cases in Europe, reporting 103 and 101 cases respectively. Britain announced 14 new cases yesterday, with 11 of those being transmitted in-country - people who had not traveled to Mexico or the United States but were infected by others who had the virus.
A pandemic could be triggered if the virus starts to be transmitted from person to person on a large scale outside the Americas, WHO experts have said. But it would have to jump among people outside schools, hospitals and other institutions that typically pass on such viruses quickly.
Chile, meanwhile, reported its first case of swine flu, a 32-year-old woman who had just arrived from the Dominican Republic.
