A New South Wales woman has been confirmed as Australia's first case of swine flu.

Queensland's chief medical officer, Dr Jeanette Young, says the woman, who is aged in her 20s, flew into Brisbane from Los Angeles on Thursday.

She says the woman was no longer contagious when she boarded Qantas flight QF16, but has since tested "weak positive" to the virus.

"We are still waiting results on four others, which we will have by the end of today," she said.

Dr Young says Queensland's medical facilities are more than up to the job of testing for swine flu.

"It's very fortunate that we've got very good testing facilities so we can differentiate between seasonal flu and this new flu ... so that we know what we need to do," she said.

"That's one of the most important things; our pathology testing at this point in time is probably one of the most critical aspects of our whole response to this flu issue."

She says more than 360 people have been tested for swine flu so far.

"We have a capacity [for] a further 300 tests at Coopers Plains, at our public health laboratory there, and then of course the private sector is very able and capable of doing a minimum 300 tests a day," she said.

Federal Health Minister Nicola Roxon told a press conference this morning authorities are contacting anyone who may have come into contact with her.

"People who were travelling on Qantas QF16 from Los Angeles to Brisbane arriving on May 7 should of course be being very conscious of any symptoms they might be showing," she said.

"The advice we have, given the history of her illness and the time when she was unwell, is that she is very unlikely to have been infectious on the plane.

"That means we are very unlikely to have any live swine flu infection here in Australia currently but we are taking all precautionary steps.

"That's why Queensland Health is following the protocols that are in place."

She says she has spoken to Australia's chief medical officer Jim Bishop, who advised that Australia should remain on the current alert level, the "delay phase".

"Because at this stage there is no evidence of any live infection in Australia, the advice currently is for us not to change that alert level," she said.

"That will continue to be assessed, of course, over the coming hours and days if there are any further developments."

Ms Roxon has asked the Australian public to remain calm.

"It was inevitable given the spread of this disease across the world that we would have some infection here in Australia," she said.

"We've got a very strong health system able to cope with this sort of outbreak, if it was to spread further in Australia.

"The border measures that were put in place by the Government have helped identify this person early and will remain in place until we're advised that these measures are no longer necessary."

She said 18 Australians are still being investigated.

Twenty-five countries are now reporting swine flu infections, with over 2,500 cases.

- ABC/AAP