Aged & Community Care Providers Association said 6000 residents and 3400 staff were infected in 1013 facilities as of Thursday.
The association's interim chief executive Paul Sadler said 10-15 per cent of staff are already isolating or quarantining at home, and the coming weeks will put intense pressure on aged care residents and workers.
"ACCPA is concerned that anywhere up to two-thirds of aged care homes could be affected by active outbreaks over coming weeks," he said in a statement on Sunday.
"The increased availability in surge workforce including the Australian Defence Force over the past week has been welcome, but there is still a shortfall.
"The reality is we can't leave older people without adequate levels of care for too long."
Mr Sadler said 2301 residents have died in 2022, including 114 in the past week.
He called for more support for a surge workforce, including ADF personnel, until at least September.
Over the longer term, Mr Sadler said, the federal government must plan to fix chronic workforce shortfalls, prepare for future outbreaks and implement reforms recommended by the recent royal commission into aged care.
"The coming weeks are critical for aged care. We must do all we can to put the protection of older people first and support our aged care workers," he said.
Meanwhile, the number of Australians who have died with the virus has surpassed 11,000.
The country's death toll rose by more than 100 on Saturday, with Victoria recording the most fatalities at 44.
NSW reported 41 deaths, while Queensland recorded eight, South Australia and the ACT three, and Western Australia two.
Tasmania also reported one death, while the Northern Territory recorded none.
The daily toll pushed the country's deaths since the beginning of the pandemic to 11,134.
As of Saturday, a little more than 71 per cent of Australia's eligible population had received three or more vaccine doses.
That was an increase of more than 9500 people on the previous day, with booster coverage among aged care residents at 95 per cent.
About 55 per cent of eligible Indigenous people have received three or more vaccine doses.
As for fourth doses, about 31 per cent of the eligible population aged 30 and over have received their winter boosters.
That figure hiked up to more than 65 per cent for those aged 65 and over.
It represented an overall daily increase for all eligible groups of nearly 91,500 people.
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