70 Aussies suspected of having swine flu

Seventy Australians are suspected of having swine flu, but the virus is showing signs of abating in Mexico where it is believed to have claimed 152 lives.

There are no confirmed cases of the virus in Australia.

The World Health Organisation (WHO) on Tuesday upgraded its pandemic threat level to four, which is two steps short of declaring a full-blown pandemic.

A phase four alert means human-to-human transmission is causing outbreaks in at least one country.

Australia has not elevated its response since the WHO announcement.

"Of course, it's of concern to us that we're now at the next phase, but we have introduced, as of last night, new border measures at our airports," federal Health Minister Nicola Roxon told ABC Radio on Tuesday.

"If we identify any cases in Australia, our response will need to change over time."

The health department learnt of the outbreak in Mexico last Friday.

Since midnight (AEST) on Monday, airlines servicing Australia from the Americas have been required to report any passengers with flu-like symptoms before being cleared to land at local airports.

Nurses are stationed at international airports to detect and treat anyone suspected of carrying the virus.

The nation's chief medical officer Jim Bishop briefed cabinet in Canberra on Tuesday.

He told cabinet Australia's stockpiled 8.7 million doses of anti-viral drugs Tamiflu and Relenza are not meant to treat every person in the country.

"We are trying to prevent the disease coming in at the moment but if we are into the business of containing the disease within small outbreaks then it will be focused in that sort of area - it won't be used for everybody," he said.

Ms Roxon said that while Australia was well placed to deal with the situation, it would be "overconfident" to say it was able to protect itself entirely.

Prime Minister Kevin Rudd vowed to use all of the government's available resources to combat the "evolving threat".

"This is a serious international concern for public health," he told reporters in Canberra.

A spokesman for the health department told AAP 70 people across the country were being tested for swine flu as at 1750 (AEST) on Tuesday.

Australia's pandemic management plan includes closure of schools and public gatherings.

Greens leader Bob Brown urged the federal government to release the pandemic plan.

"We need to know that the government recognises that if there's a pandemic we can't prevent it coming to Australia," he said.

"It's going to have everybody worried, anxious. It's going to require everybody to be well informed and know what to do.

"We need the information from government - it's coming out slowly but they ought to have been faster."

Mexico's Health Minister Jose Angel Cordova signalled on Tuesday the epidemic may be abating because the daily number of suspected flu deaths had gone from six on Saturday to five on Sunday and to three on Monday, he said.

A WHO-accredited laboratory in Melbourne is testing samples from 10 high school students for swine flu after they returned to Auckland from Mexico on Saturday.