Cases in the nation’s three most populous states have more than doubled in the space of two weeks, although the number of serious infections remains low.

NSW, Victoria and Queensland reported 58,373 new infections on Friday, up from 42,264 the previous week and 27,103 two weeks ago.

Health authorities in NSW, Queensland, Western Australia and the ACT are asking people to return to wearing masks in public indoor areas and on public transport, although they have stopped short of reintroducing mandates.

Despite the rising case numbers, only 50 people were in ICU with the virus in the three states as of Wednesday.

The figures represent a fraction of those recorded during the peak of the previous COVID wave in July.

Earlier in the week, federal health minister Mark Butler said the government’s vaccine advisory body didn’t recommend rolling out a fifth vaccine dose or third booster despite a caseload rise.

He said the group noted an extra booster was unlikely to reduce the fourth wave.

Carnival Cruises has made mask-wearing compulsory again on its liners after a spate of onboard cases.

Management said the health measure would return out of an abundance of caution due to the evolving public health situation.

The measure was scrapped for passengers in February and for staff last month.

Meanwhile, a study on the impact of the first NSW COVID-19 lockdown on almost 900 kids and carers in out-of-home care found restrictions had a great effect on young people’s education, behaviour and social and physical activities, as well as time spent with birth families.

It had a huge bearing on carers’ financial situations as well as their access to services and support.

However, research published by the University of Wollongong, University of Canterbury and University of NSW shows some families still had a positive experience.

Twice as many children reported a positive experience than negative one, which the authors said backed up other studies suggesting the first lockdown allowed children with complex needs to access greater emotional support and a sense of security.

“It may also be that the restrictions provided some children with an opportunity to develop stronger relational ties with their carers,” they noted.

WEEKLY VIRUS DATA BY JURISDICTION:

* NSW: 27,869 cases, 39 deaths

* Victoria: 20,398 cases, 46 deaths

* Queensland: 10,106 cases, 15 deaths

* South Australia: 8346 cases, three deaths

* ACT: 1194 cases, no deaths

* Northern Territory: 286 cases, no deaths.