The head of the World Health Organization quizzed health officials from several nations in a conference call Wednesday, asking about a recent spike in swine flu cases that may show the world is already in a global epidemic.

WHO spokesman Thomas Abraham confirmed that Director-General Margaret Chan was speaking to "seven or eight" countries but was unable to name them.

However, the list was likely to include Australia, Britain, Japan, Spain — countries that have seen a recent spike in cases indicating that the virus is taking hold there.

Chan says she personally believes that a pandemic is under way, but will be seeking clear proof that the new A(H1N1) virus is spreading rapidly from person to person outside the Americas before declaring a global epidemic.

"Once I get indisputable evidence I will make the announcement" she told reporters on Tuesday.

So far, over 26,500 people have been infected worldwide and about 140 have died of swine flu.

Australia has reported a sharp rise in cases since last week — to 1,260 by late Wednesday. Australian authorities say many cases cannot be traced back to travelers or common infection sites such as schools, indicating that — like in Mexico, the United States and Canada — the virus is becoming entrenched in communities.

Britain has reported 675 cases, but some outside health officials believe the country is not looking very hard for swine flu In recent weeks, three Greek students have returned home after catching swine flu in the U.K., proof the virus is spreading more widely than British authorities admit.

Britain's Health Protection Agency denies that swine flu is established in communities, but some health officials have published reports showing the virus is so widespread it is being exported to other countries. Last month, an article in the journal of the European Centre for Disease Prevention and Control detailed the case of the Greek students.

WHO spokesman Dick Thompson said WHO has seen media reports from several countries suggesting there are many more cases or wider transmission of the virus, but that the countries themselves are not reporting these cases.

"We're trying to resolve that conflict," Thompson said. "There could be an explanation that's not obvious, but we're trying to put the question directly to officials about why there are these differences in the numbers of cases being reported."

If swine flu is spreading rapidly from person to person beyond the Americas, this should trigger the conditions for WHO to declare a pandemic. But despite reports of hundreds of swine flu cases in Europe, Japan and Australia, the agency has dragged its feet on announcing a global outbreak.

Thompson said if WHO learns there is widespread transmission of swine flu, the agency may move quickly to declare a pandemic.

Many countries have asked WHO to hold off on such a declaration, fearing their citizens will be alarmed and confused and governments will be pressured to institute costly and often ineffective measures like trade and travel bans.

But WHO insisted that a pandemic declaration would not mean the situation was worsening.

"It does not mean that the severity of the situation has increased and that people are getting seriously sick at higher numbers or higher rates than they are right now," WHO's flu chief Keiji Fukuda said Tuesday.

Fukuda said the fact that half of the fatal cases occurred in otherwise healthy adults was a cause for concern, but noted that the virus appears to mostly be causing a mild illness.

"Most of the people who have gotten infected have self-limiting illness which can be taken care of at home, or without specialized medical care and these people recover," he said.