A nurse in Yogyakarta, Indonesia, holds a box of the antiviral drug Tamiflu, which is effective in combating swine flu if the treatment is given early enough. (Slamet Riyadi/Associated Press)

The World Health Organization said Thursday it has begun distributing a stockpile of antiviral drugs to a number of countries, as Mexico's top health official said the number of new cases of swine flu in the country is stabilizing.

Dr. Keiji Fukuda, WHO's acting assistant director-general for health security and environment, told reporters the drugs would be distributed to countries "in most need," especially developing countries that are least prepared to contend with a potential pandemic.

Fukuda added there was no evidence as of Thursday to suggest the UN health agency should raise its pandemic alert to the highest level.

Meanwhile, Mexico's top epidemiologist said the WHO was slow to react to the outbreak, and he wants an investigation.

In a telephone interview with The Associated Press from Mexico City late Thursday, Dr. Miguel Angel Lezana said he is troubled by the response of the Pan American Health Organization, or PAHO, and its parent organization, the WHO, in the early days of the outbreak.

Lezana, director of the National Epidemiology Center, said it notified PAHO on April 16 about the outbreak in Mexico, but that action wasn't taken until eight days later, when the WHO announced the spreading epidemic.

Health officials in Mexico were still contending with a backlog of several thousand specimens that need to be tested, Fukuda said.

"The investigations in Mexico are looking at a very large amount of data," he said. "Right now, I think that mainly what is needed is time by the investigators to take a look at the disease cases."

Fukuda said the global stockpile of the drug Tamiflu began in 2005 after the drug manufacturer, Roche Laboratories, donated five million units to the UN health agency. He added that the manufacturer is stepping up production of the drug.

The WHO also said it will stop using the term "swine flu" to avoid confusion over the danger posed by pigs. The agency will now refer to the disease by its scientific name — H1N1 influenza A.

WHO spokesman Dick Thompson said the name change comes after the agriculture industry and the UN food agency expressed concerns that the term "swine flu" was misleading consumers and needlessly causing countries to order the slaughter of pigs.

Outbreak stabilizing: Mexican official

In Mexico City Thursday, Mexican Health Secretary Jose Angel Cordova told a news conference he hoped the stabilizing trend will continue and that a vaccine would be available in six months.

However, Fukuda, reacting to similar comments from other Mexican officials, quickly cautioned case numbers in Mexico will fluctuate, adding the WHO had had yet to see concrete evidence that swine flu was levelling off in Mexico.

Fukuda said the number of confirmed cases of the H1N1 virus in Mexico had jumped to 97 from 26; seven deaths have been confirmed.

"It's a mixed pattern out there," Fukuda said. "What's happening in one part of the country is not necessarily what's happening in another part of the country."

The U.S. Centers for Disease Control and Prevention reported 109 laboratory-confirmed cases in 11 states, while the death toll in the U.S. remained at one. Canada has at least 34 confirmed cases and no deaths.

Other figures from Mexico suggest there have been 160 other suspected deaths, with about 2,955 suspected to have fallen ill from the virus. Fukuda said the WHO only lists deaths the agency has confirmed in its laboratories.

Obama team member had flu

Dr. Richard Besser, the CDC's acting director, said Thursday he expects U.S health officials will continue to see a "broad spectrum" of the disease in more patients, ranging from milder infections to severe illnesses.

His comments come as White House officials said Thursday a member of the advance team sent to Mexico to plan U.S. President Barack Obama's recent visit to the country experienced flu-like symptoms, along with three of his family members.

White House press secretary Robert Gibbs said all four had probable swine flu and have since recovered.

Gibbs said the man, who was not named but identified as an aide to Energy Secretary Steven Chu, did not come within two metres of Obama and did not fly on the president's plane.

Gibbs remained steadfast that the president was never at risk of contracting the flu.

EU countries reject Mexico flight ban

In Luxembourg, European Union health ministers holding an emergency talks on swine flu agreed to work "without delay" with drugmakers to develop a pilot vaccine to fight the virus.

They also rejected issuing a Europe-wide travel advisory for Mexico, where the outbreak is believed to have originated. Officials did say they could reconsider the option in the future.

Many EU nations have already warned travellers to avoid unnecessary trips to Mexico and parts of the United States where outbreaks have been confirmed.

French Health Minister Roselyne Bachelot had said she would push on Thursday for the EU to suspend flights to Mexico.

Her German counterpart said, however, "that would be a very drastic measure.

"At the moment, I don't think the situation is there; whether it could be will depend on how things develop," German Health Minister Ulla Schmidt said on ARD television Thursday morning.

WHO officials have said it's already too late to contain the virus through travel restrictions.

Tour companies being careful

The WHO has not called for travel restrictions or border closures. However, several cruise lines, tours and flights destined for Mexico have been cancelled, including several operated by Air Canada, WestJet and Transat.

Ecuador, Cuba and Argentina have banned travel to or from Mexico.

WHO raised its global pandemic alert level to five, its second-highest level, on Wednesday. Phase 5 is called when there is human-to-human spread of a virus in at least two countries in one region, according to the WHO's pandemic response guidelines.

The classification means a pandemic is imminent and countries must finalize preparations to deal with the outbreak of swine flu, officials said.

With files from The Associated Press