A top World Health Organization (WHO) official has said that the health watchdog has no evidence of sustained community spread outside North America.
Dr Michael Ryan, WHO Director of Global Alert and Response, also praised European nations' handling of cases and said events did not seem out of control.
AdvertisementMexico has cut its suspected death toll by 75 to 101, indicating the outbreak may not be as bad as initially feared.
The country has ordered a five-day shutdown in a bid to contain the virus.
Mexican Health Minister Jose Angel Cordova told the BBC that, based on samples tested, the mortality rate was comparable with that of seasonal flu.
"I think it would be, at this stage, unwise to suggest that, in any way, those events are out of control or spreading in an uncontrolled fashion," the BBC quoted Ryan, as saying.
"At the present time I would still propose that a pandemic is imminent because we see the disease spread," Dr Ryan added.
The WHO is sending 2.4 million courses of antiviral treatment to 72 nations around the world, Dr Ryan said, among them many developing countries.
But in cases of the virus outside Mexico, the effects do not appear to be severe.
Italy and the Irish Republic reported their first cases on Saturday, bringing the number of countries affected to 18.
Canada has announced that a herd of pigs has tested positive for swine flu.
A senior agriculture official told a news conference that a farm worker who fell ill after returning from Mexico last month might have infected the pigs.
In Egypt, authorities have begun in earnest the slaughter of more than 300,000 pigs, in what was originally described as a precaution against swine flu.
Officials now say the move is a general health measure aimed at restoring order to Egypt's pig-rearing industry.
International experts say there is no scientific rationale for Egypt's pig cull
Experts say the virus cannot be caught from eating pork and there is no scientific rationale for the cull.
Five countries outside Mexico have confirmed person-to-person transmission.
China is trying to stop the spread of the virus, after getting its first case on Friday.
It says it will quarantine all those who travelled on a flight from Mexico with a man suffering from swine flu.
Flights from Mexico have been suspended, and fellow guests and staff at the Hong Kong hotel where he was staying have been quarantined.
On Saturday, Mexico's foreign minister advised citizens not to travel to China to avoid the health measures being taken there against
The US has now confirmed 160 cases of swine flu across 21 states but has seen only one death, of a Mexican toddler in Texas.
President Barack Obama said in his weekly radio address that the US was taking "all necessary precautions" to ensure it was prepared if the virus developed into "something worse".
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