O-Week activities coincided with an increase in cases in the residential halls, which reached more than 200 by Sunday night.

Chief Operating Officer Paul Duldig refused to say how many students from the 5500 students residing on campus had tested positive on Monday.

"What we're doing at the moment is leaving the case number recording to ACT Health just to avoid confusion, but we can say that of those students, less than 10 per cent are currently testing positive," Mr Duldig said.

The sickest students will be moved to ACT Health quarantine facility, some will go to self-contained units on campus and mild cases will remain in their residences.

Mr Duldig said a team of 25 people was working on providing food and essentials to students in quarantine and doing wellbeing checks.

University of South Australia professor of biostatistics Adrian Esterman said the risk of the virus spreading through university residences would depend on mask wearing rules, ventilation and the vaccination status of residents.

"It wouldn't at all surprise me if it went through a residential setting. The real issue is does it matter? Students in their 20s and 30s generally speaking, unless they've got some underlying health condition, aren't going to get very sick, especially if they've been vaccinated," Professor Esterman said.

"There'll be a certain percentage, and it will be somewhere between 10 and 30 per cent, who end up with long term health problems. You don't really want that."

Meanwhile, the University of Canberra has six active cases out of the 1560 students living on-campus.

Most of the students at University of Canberra arrived in late January in time for Orientation Week from January 31.

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A University of Canberra spokeswoman said a vaccine mandate applied to all residents, visitors and staff at the on-campus residences.

ANU has not made a decision on a vaccine mandate.

Mr Duldig said face-to-face classes would continue amid the outbreak in residences.

"We don't see any reason why case numbers in the halls will impact on us being able to teach on campus. It would really be a much broader community concern to make us reconsider that."

The ACT recorded 583 new COVID cases on Tuesday as it marked 12 months since the first vaccination was administered.

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