The relaxed rules came as COVID case numbers almost doubled in the territory, with 946 new cases reported on Wednesday. This was up from 583 on the previous day.

It was the highest daily tally in more than a month with the jump in cases driven by a major outbreak in student residences at the Australian National University.

Mandatory indoor mask requirements will be ditched in most places in the ACT from this weekend. Masks will still need to be worn in certain places including on public transport, taxis or rideshare services, hospitals, aged care facilities and at Canberra Airport.

Staff and visitors to schools will also be required to wear masks. Students in year 7 to 12 will also continue to wear masks.

Other workers who will need to wear masks are people who provide services to a person with a disability and in-home and community aged care providers. The new rules come into place from 6pm on Friday.

However, ACT chief health officer Kerryn Coleman has strongly urged people to continue wearing masks in indoor settings where physical distancing is difficult.

"Mask wearing has been a really, really important part of minimising virus transmission," she said.

"So while we are easing the majority of our mandatory requirements, I really strongly encourage everyone to continue considering wearing a mask when you go indoors to public settings, particularly where you think it will be hard to physically distance."

Dr Coleman said she would continue to wear masks in places such as supermarkets or at restaurants and cafes when she was not seated.

She also recommended that businesses implement policies around mask wearing to suit their particular circumstances, especially businesses with customer-facing roles.

"So we now actually need businesses and workplaces to really consider their own circumstances and what things look like in their own operations. How best do you need to use masks to protect your employees, but also your clients as those people who come in and receive a service from you," Dr Coleman said.

The changes will bring the ACT largely into line with mask wearing requirements due to come into place in NSW and Victoria. The changes are also a complete backflip on comments made earlier in the month by Health Minister Rachel Stephen-Smith who said mask rules were likely to be in place until the end of winter.

Dr Coleman indicated the NSW decision have an impact on the ACT's situation. She said she had been in discussions with NSW chief health officer Kerry Chant around how to balance public health considerations and the need for mandates.

She said based on current circumstances she felt comfortable with mask wearing being only a recommendation and not a requirement.

"As we've talked about before, we have very porous borders with NSW and it is very difficult to have different settings for people who cross the borders every day," she said.

"Kerry and I talk a lot about what we're going to do and how we're going to do that. And one of the things we discussed together is how to balance this onus on people's lives mandates are not easy... I have to make a serious consideration when you mandate someone to do something rather than recommend.

"With the severity that we're seeing with the Omicron variant. I am very comfortable that the recommendation is in place rather than the mandate."

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Ms Stephen-Smith again warned on Wednesday that the situation could change quickly and warned the winter period would be challenging. This is likely to be exacerbated by the seasonal flu, which has not occurred in Canberra in large numbers since the start of the COVID pandemic.

"We know that Canberrans have generally really responded to the ACT government's response to the pandemic and supported that response," she said.

"There will always be people who think that we've gone too far or that we haven't gone far enough and there's always a balancing act when we talk about public health restrictions."

"We do need to remind people that the situation can change very quickly."

"We expect to see changes through the winter period and we've watched very closely what's happening in the northern hemisphere over their winter."

While case numbers have risen, Dr Coleman said she was pleased that hospitalisation numbers were not going up.

There were 40 people in hospital in the 24 hours to 8pm on Tuesday. Two people were in intensive care but neither required ventilation.

An outbreak at the ANU has continued to grow and Dr Coleman said this had driven an increase in cases but most of the territory's recent cases have been in people under 18.

"The majority of the extra cases are in our 5 to 11 and then our 12- to 17-year-old age group and reflect schools going back," she said.

"Today we have seen a few more cases in our adult age group which reflects the known ANU outbreak that we are seeing at the moment.

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