The chief of WHO's flu program, Keiji Fukuda, says that, "we are at Phase 5 but are getting closer to Phase 6." The disease has spread to 64 countries and infected 18,965 people, causing 117 deaths. Its spread in Australia, Chile, Japan, Spain and the United Kingdom, in particular, has moved the world closer to Phase 6 -- the top level pandemic alert.

"There are a number of countries that appear to be in transition, moving from travel-related cases to more established community types of spread," Dr Fukuda said. "They include countries such as the UK and Spain in Europe, Japan in Asia, Chile in South America and also Australia."

Fukuda says the global body is now calling the situation "moderate" rather than "mild" because it is still unclear how serious the virus is. He stated that WHO has consulted experts on when to declare the outbreak a pandemic — a global epidemic. Those experts have advised that the severity of the virus should be considered instead of only its geographic spread.

In the U.S., cases of the new H1N1 flu virus have now been found in all 50 states and tests confirmed the virus in more than 10,000 people across the nation. Public health experience suggests that confirmed infections represent about one in 20 of the actual number of infections, which would bring the total number of cases in the U.S. to around 200,000. To date, seventeen deaths in the United States have been linked to the swine flu virus.