The World Health Organization last declared a pandemic 41 years ago
A sharp increase in swine flu cases in Australia may mean the infection has become a pandemic, the World Health Organization says.
For that to happen, officials would have to verify that the disease had become established outside North America, where the crisis began.
"Once I get indisputable evidence, I will make the announcement," said WHO director general, Margaret Chan.
More than 1,200 people have contracted the virus in Australia - none fatally.
The total means Australia has seen a four-fold increase in a week.
Less than a month ago the country had only a handful of cases of the H1N1 virus but it now has the highest number of infections outside North America.
Victoria and the state capital, Melbourne, are the worst-hit with more than 1,000 confirmed cases.
Most of those affected are suffering only a mild illness, but the Health Minister of Australia's Queensland state, Paul Lucas, has warned that the contagious respiratory condition would inevitably claim lives.
The head of the WHO's global influenza programme, Keiji Fukuda, said the situation had "evolved a lot" in recent days.
"We are getting close to knowing that we are in a pandemic situation," he said.
But Dr Fukuda urged calm. "It does not mean that the severity of the situation has increased or that people are getting seriously sick at higher numbers or higher rates than before," he said.
Following the major outbreaks in North America the flu alert is currently at phase five of a six-level scale.
The virus has infected more than 26,500 people in 73 countries.
The WHO held a conference call with governments on Wednesday, but afterwards said no decision had been taken on moving to phase six - the pandemic stage - at the moment.
Gregory Hartl, WHOs spokesperson for epidemic and pandemic diseases, said if a pandemic was announced it would not be the "apocalyptic situation" envisaged when bird flu looked liked it would be the cause.
"What we are seeing now with H1N1 is that in most cases the disease is self-limting, lets say 98-98% of the people we know to be affected recover without any need for hospitalisation, as far as we can tell.
"We do understand that the natural reaction of people if and when we declare phase six could be very strong.
"But we would hope that there would be quiet quickly an adjustment reaction, as happened in the US, when people realised they weren't getting seriously ill."
BBC medical correspondent Fergus Walsh says it is true that the word "pandemic" sounds scary. But it simply means a global epidemic of an infectious disease.
He says it is not a signal that the virus is getting more virulent - only a measure of its geographical spread.
As the number of H1N1 cases in Australia passes 1,200, Singapore has urged its citizens to avoid travel to Victoria.
Authorities in New South Wales and South Australia, as well as the national capital, Canberra, have told children who have recently travelled to Melbourne to stay away from school for a week on their return home.
The entire squad and staff of the Brisbane Broncos rugby league club have been put into quarantine as tests are carried out on a player suspected of contracting swine flu.
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