The outbreak of swine flu in a number of countries is definitely "more worrying" than bird flu, an Australian infectious diseases expert says.
Professor Paul Kelly, from the Australian National University, says while pig flu appears less deadly than avian flu, that fact will actually help it spread faster.
"It doesn't seem to have as high a fatality rate as avian influenza but it does seem to be more easily spread and rather rapidly," Prof Kelly told ABC Radio.
"In terms of an epidemic, for the virus to be able to spread it's actually better for the virus for humans to remain alive because that can spread it more quickly and to a greater extent."
The World Health Organisation has warned the new influenza strain is thought to have killed 103 people in Mexico and affected about 1,600 others.
There are also 20 confirmed cases in five US states and suspected cases in Canada, France and New Zealand.
Prof Kelly was on a teaching trip to New Zealand when 10 high school students returned from Mexico on Saturday with flu-like symptoms.
He was called on by the government to help investigate.
The students have since tested positive for influenza A and are likely to have swine flu.
"Swine flu appears to be. . . a new strain which appears to be spreading from human to human and that is very concerning," Prof Kelly said.
"What appears to have happened is what we've been concerned about for a number of years, of different strains of flu from different animals combining and transferring into a flu strain that is transmissible between humans."
Bird flu has killed nearly 300 people since 2003.
Those killed by bird flu contracted the virus after coming into contact with infected poultry.
Prof Kelly said while swine flu had claimed many lives in Mexico, there had been no deaths elsewhere.
Those killed have been generally young and otherwise healthy.
"It's not the typical people that are a greatest risk during a normal flu season."
The good news is the strain seems "sensitive" to antiviral drugs Tamiflu and Relenza, Prof Kelly said.
Vaccination was another plank in Australia's defence, and people should have a flu shot, even though the standard vaccine is thought to be "not suitable" against swine flu.
"At this stage in Australia there's no need to panic or to consider major public health messages."