South Australian authorities are "extraordinarily concerned" about the presence of the Omicron COVID-19 variant interstate, but will not make any immediate changes to the state's borders.
Premier Steven Marshall has instead indicated travellers from NSW, Victoria and the ACT could soon find themselves locked out of SA, only days after they were welcomed back for the first time in months.
"It may become necessary. I hope it doesn't," he said in a press conference on Saturday, before SA reported five new cases.
"We would only do that if we wanted to make sure that we still enjoy a Christmas here in SA. This is a balancing act."
Chief Public Health Officer Professor Nicola Spurrier on Saturday morning recommended to the state's COVID-19 directions committee that borders be shut.
"Clearly when you have something that is unknown, the lowest risk would be to try and keep it out for as long as possible," she said.
But instead the committee agreed to require all arrivals from NSW, Victoria and the ACT be tested upon arrival.
They must isolate until a negative result is received - which currently takes about five hours, Mr Marshall said - and be tested again on day six of their visit to SA.
The new rules are in addition to a requirement for travellers from those parts of the country to present proof of a negative test undertaken up to 72 hours before their arrival.
"We're going to put as many speed bumps in the way of the Omicron variant while we gather more information as to whether or not this really is a very different situation going forward," Mr Marshall said.
The premier rejected suggestions the government was being indecisive on borders.
The state is managing the transmission of the Delta COVID-19 variant as expected but Omicron is a "game changer", he said.
"This has got nothing to do with Delta, it has got everything to do with the Omicron variant," Mr Marshall said.
"We remain extraordinarily concerned about the Omicron threat."
Prof Spurrier said the health team is particularly concerned about vaccine efficacy against the new strain, the severity of the variant, and high rates of reinfection observed abroad.
Concerns over community transmission in Sydney, and the ability for overseas arrivals to make their way into SA also remain.
Some other jurisdictions only require international arrivals to quarantine for 72 hours, or allow them to immediately travel to other places in Australia.
Under current rules, all international arrivals in SA must quarantine for 14 days.
South Australia this week reported its largest single-day tally for more than a year, with the current outbreak forcing the governor and the opposition leader into isolation.
A further five infections were recorded on Saturday among a man in his 50s, three women in their 30s, 50s and 60s and a child.
Australian Associated Press
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