A total of 25 cases have now been confirmed, including two young boys from the cruise ship, the Pacific Dawn, in Sydney overnight.
"We are moving into a different phase here in Australia; the disease will be spreading quickly," Ms Roxon said.
"We know with the increased number of cases that there will be increased contact, that there will be more people who will be confirmed with having swine flu.
"We need to put all our effort into making sure that is a small number, as small as we can keep it."
Victoria has 14 confirmed swine flu cases, NSW five, South Australia and Queensland two, ACT and Western Australia one.
What a different story, only 8 days later, and these are only the confirmed cases. The real number must be ten times this:
There are now 521 cases of swine flu in Victoria, an increase of 126 overnight.
NSW has 70, Queensland's swine flu tally has risen to 26, Tasmania has two cases, South Australia eight, ACT four, Western Australia two and the Northern Territory one.
Around the rest of Australia, Victoria now sits in the same category as countries such as Mexico, Panama and Japan.
NSW, Queensland and South Australia all announced the move on Wednesday, with Queensland authorities saying Victoria's status warranted further containment measures.
The announcement will affect hundreds of Queensland and NSW families who have flown to Melbourne for the State of Origin rugby league match on Wednesday night.
On Wednesday, Victoria changed its pandemic status from contain to a modified sustain level.
How did it happen? Here is one way, the Pacific Dawn, a cruise ship affectionately now called the "Plague Ship" by some.
The Pacific Dawn is currently cruising up the Queensland coast with a new load of passengers after docking in Sydney on Monday when it was the centre of a swine flu alert.
On the cruise into Sydney, flu-like symptoms were reported by 172 passengers - five of whom were Queenslanders who subsequently tested positive for the disease.
