SYDNEY - Australia is facing a fresh Covid-19 outbreak from new strains that are surging across the country just as the summer holidays are set to give a much-needed boost to the tourism and hospitality sectors.

Less than a month after Australia ended a mandatory five-day isolation for Covid-19 cases, there have been calls to reintroduce restrictions such as compulsory mask-wearing.

The country’s chief medical officer, Professor Paul Kelly, said this week that an outbreak involving Omicron variant XBB is already under way. He said lockdowns are unlikely, urging people to ensure they are fully vaccinated and to stay home if unwell.

“All indications are that this is the start of a new Covid-19 wave in Australia,” he said in a statement. “This was to be expected and will be part of living with Covid-19 into the future.”

The state of Queensland – a popular tourist destination – moved to recommend masks on public transport and in other indoor settings from Friday, after lifting its level of Covid-19 alertness to the second highest of its three levels.

In the past week, the state experienced a 32 per cent increase in new cases from the previous week – from 4,427 to 5,828 – and a near doubling of the number of Covid-19 patients in hospital, from 105 to 203.

“The fourth wave that we have been expecting, now, we believe, has arrived,” Queensland Premier Annastacia Palaszczuk told reporters. “No one should be alarmed. We have been living with this virus for a long time, and Queenslanders know what to do.”

New South Wales, the most populous state, also declared that it was in the grip of a fourth wave, after new cases leapt in the past week to 19,800, up from 12,450 cases a week previously.

Victoria, Western Australia and South Australia have all reported surging case numbers.

The outbreak largely involves Omicron sub-variants, including XBB and another new strain BQ.1. The sub-variants are believed to be highly contagious but not more harmful than previous strains.

In addition, much of the population has some degree of protection after being vaccinated or experiencing Covid-19, or both.

Australia has recorded 15,790 Covid-19-associated deaths since the start of the pandemic.

But the outbreak comes just as the country had all but moved on from Covid-19. It began removing restrictions from late last year, after imposing one of the strictest lockdowns during the peak of the epidemic.

City centres are now bustling, and airlines and hotels are at capacity. States no longer provide daily Covid-19 updates, and the pandemic had – until recent days – slipped out of news headlines.

Some experts have called for the reimposition of restrictions such as mandatory mask-wearing indoors, though the authorities believe the worst of the outbreak will likely be over by the start of the Christmas holiday period.

Professor Adrian Esterman, a public health expert from the University of South Australia, said mask-wearing in shops and other indoor areas should be made mandatory.

“We’ve removed all our public health measures, and we don’t have any brakes to put on transmission at the moment,” he told ABC News.

But the authorities have so far been reluctant to revert to compulsory measures.

“We’ve seen these same variants go through other countries, most recently Singapore,” Prof Kelly told Channel Seven. “They had a very quick, sharp wave of cases, but not a lot else, and then they moved on.”