South Australia is battling to prevent a serious COVID outbreak turning into a second wave, as several states slam restrictions on their borders to prevent the import of cases from SA.

The outbreak is a setback the goal of having most of Australia open by Christmas – although Scott Morrison on Monday was quick to say he hoped it would not stymie that timetable.

Queensland, Tasmania, and Western Australia as well as the Northern Territory announced border clamps on travellers from SA. In WA’s case it had only just eased restrictions for them. WA and Tasmania are banning arrivals from SA generally; Queensland and the NT have specified local government areas.

NSW and Victoria are leaving their borders open. Victoria will impose health checks on people flying into Melbourne from Adelaide.

SA on Monday announced 18 new cases, in people aged from one through to their 80s. Thirteen of the cases are linked to a Parafield Gardens cluster.

The outbreak started from hotel quarantine. A hotel worker and two security guards have tested positive. The worker spread the virus through a large family.

The SA outbreak and the reaction of various states once again shows the split between leaders over the issue of “living with COVID”.

Morrison and NSW Premier Gladys Berejiklian argue small numbers of cases can be managed while the economy, and borders, remain open. But several state leaders take more conservative approaches, confident they have the support of their populations.

The SA outbreak will test the effectiveness of the state’s contact tracing. The federal government last week released the report of chief scientist Alan Finkel, who found states’ systems were now generally sound while recommending some improvements.

SA premier Steven Marshall said: “Time is now the essence and we must act swiftly and decisively”.

“We will throw absolutely everything at this to get on top of the cluster.” He said the next 24 hours would be critical.

The SA government is closing gyms, recreation centres, and trampoline/play cafes for an expected two weeks. Community sports fixtures and training are also cancelled.

Among a range of caps, gatherings at private residences will be limited to 10 people.

All international flights to Adelaide are suspended for the rest of the week.

The state’s chief public health officer, Nicola Spurrier, said “What we are facing is, indeed, a second wave but we haven’t got the second wave yet. We are in very, very early days.”

AnglicareSA said two employees from its Brompton aged care home had tested positive to COVID-19 on Sunday.

The workers hadn’t been at Brompton since Friday 13 and had not worked at any other AnglicareSA residential aged care home.

On Friday national cabinet committed to having internal borders – apart from WA’s – open by Christmas.

Morrison said on Monday: “It is not a surprise that [an outbreak] can occur from a quarantined facility. What matters is how you respond in these situations”.

Acting Chief Health Officer Paul Kelly said he was confident the systems were in place to deal with this outbreak.

The Australian Health Protection Principal Committee held an emergency meeting on Monday.

Asked about the different responses between NSW and WA on borders, Morrison said the AHPPC had not recommended collectively any one response.

“What is important is these don’t get sort of locked in as part of another enduring disruption and as soon as South Australia is able to get on top of this I would be expecting that states would keep on the path that we have set towards Christmas.”

After the disastrous consequences of Victoria’s second wave for residential aged care, with residents accounting for most of the deaths, Morrison said: “We have stood up the aged care response centre in South Australia. That is important to ensure that we deal with any potential risks or issues in residential aged-care facilities. I particularly spoke to the premier about that today”.

Addressing a Committee for Economic Development of Australia dinner on Monday night, Reserve Bank Governor Philip Lowe highlighted the link between what happens on the health front and the trajectory for the economy.

“There is still considerable uncertainty about the [economic] outlook,” he said.

“If we do get further good news on the health front, we could have a rapid rebound.

"At the same time, it is still possible that we experience further outbreaks. And the hoped-for medical advances may be delayed and could face production and distribution challenges slowing their rollout. This means that there are downside scenarios too.”