Australia said four swine flu victims had been admitted to intensive care wards on Thursday, as world health chiefs considered whether the outbreak warranted declaring a global flu pandemic.
Australia's A (H1N1) tally ticked up by 39 to 1,263 cases, with rugby league player Karmichael Hunt the latest high-profile athlete to contract the virus that threatens to throw the country's sporting schedule into chaos.
The vast majority of cases, 1,011, were in the southern state of Victoria, where authorities said four people were being treated in hospital intensive care wards.
It was a potentially worrying escalation for Australian health chiefs, who have previously reported only mild symptoms among swine flu victims, and no recorded fatalities.
The World Health Organization (WHO) said Wednesday that Australia was on a list of countries it was closely monitoring for "undisputable" evidence of domestic human transmission.
That would edge authorities closer to declaring a global swine flu pandemic, a move one WHO official said this week was "very, very close".
"We are very mindful of what is going on in Australia and a number of other countries, and I will simply say that we are getting closer (to declaring a pandemic)," WHO assistant director-general Keiji Fukuda said.
Swine flu has spread rapidly in Australia, the world's fifth worst-hit country, since sick passengers were allowed to leave a cruise ship in Sydney late last month.
Victoria has recorded numerous cases of domestic transmission, which occurs when the virus spreads between people within a community, rather than the infection being driven by people coming from overseas.
The state lifted its swine flu status to "sustain" last week, meaning it no longer tests for every suspected case, concentrating only on patients considered high risk.
Hunt and another rugby league player Ben Hannant both contracted the virus when they
played in the elite State of Origin match in the Victorian capital Melbourne last week.
All players involved in the game have since been placed in quarantine and there are questions about whether some National Rugby League (NRL) matches will have to be cancelled.
The NRL decided it will push on with a key match between Hunt's Brisbane Broncos and the Canterbury Bulldogs Friday after consultations with health authorities.
Swimming Australia cancelled a national competition scheduled to be held in Melbourne later this month, saying it could not risk its athletes catching the virus.
The WHO says 74 countries have reported 27,737 cases, including 141 deaths,since the A(H1N1) virus was first discovered in the United States and Mexico in April.