The World Health Organisation is on the verge of declaring a pandemic because of the rise of swine flu cases in Australia.
So far more than 1,200 cases have been diagnosed there, and the rapid spread of the virus in a region outside North America is considered the key factor in raising the alert to the highest level.
But the world body's deputy chief, K J Fukada, says the organisation does not want people to panic.
The alert level is expected to be raised within days.
The World Health Organisation's director-general, Margaret Chan, believes that "on the surface of it" a pandemic has been reached.
Ms Chan is to hold a conference call with governments to verify some of the reports she has received before making a formal announcement.
World Health Organisation Dick Thompson says health officials worldwide will have to watch the swine flu virus for a year or even two.
Mr Thompson says influenza viruses always change.
The swine flu virus has been mild in most people, but half of those it infects are young and healthy, he says.
More than 1,200 cases have been confirmed in Australia, more than 1,000 of them in Victoria.
The NRL clash between the Brisbane Broncos and the Sydney Bulldogs on Friday could be called off because of swine flu.
The entire Broncos team is in quarantine, waiting to see whether player Karmichael Hunt tests positive for the virus.
Swine flu has so far infected 26,563 people in 73 countries and caused 140 deaths.
Twenty cases have been confirmed in New Zealand.
