Warnings new COVID-19 strains could be brought in by travellers

“But of course we will and we have looked at what those exposure sites are in New Zealand and we’ll be looking at that for anyone coming across the border from New Zealand,” Professor Kelly said.

“As we know, they have had the South African strain come out of the quarantine facilities in New Zealand and maybe that could be the UK strain, we don’t know yet but those things are ongoing.

“The important point is that we’re very closely associated with that information coming straight to us from the authorities in New Zealand as it happens.”

He said his state colleagues had asked for the manifests of all flights from New Zealand that had come into Australia over the past few days.

A Department of Health spokesman said there was no specific threshold applied in regards to maintaining the travel bubble and “any future decisions would have regard to epidemiological and other relevant context to inform decisions proportionate to risk.“

Caps on international arrivals in a number of states, including NSW, are also set to return to previous levels on Monday after being cut by half in January following the emergence of a highly contagious strain of the virus in the UK.

Weekly arrivals were capped at 1050 in NSW, 500 in Queensland and 512 in Western Australia for a month, after a national cabinet meeting on January 8.

On Monday, those caps will return to previous levels of 3010 people a week in NSW and 1000 people in Queensland. Western Australia’s cap will remain at 512.

However, Victoria has temporarily stopped accepting international arrivals during its lockdown. Its cap was originally due to increase from 1120 to 1310 on February 15.

Epidemiologist and lecturer in international health at the University of NSW Abrar Ahmad Chughtai said increasing caps on arrivals will increase the risk of introducing new variants of the virus to Australia.

“We’ll need to be very careful, we’re relying more on hotel quarantine now than ever before,” he said.

“I’m sure health authorities have got in place more facilities, more staff, more masks and cleaning and hygiene processes ahead of the increase.

“As long as you’re managing these things, it’s probably the right decision. People are stuck overseas and need to come back.”

A NSW Health spokesperson said strong arrangements were in place between multiple government agencies, including NSW Police, to effectively manage the return to the previous daily arrivals cap.

NSW’s 28-day milestone came amid new requirements that anyone who returned to NSW from Victoria after midnight on Friday, February 12, must comply with the five-day “circuit-breaker” lockdown in place in Victoria after more than a dozen cases were linked to a cluster originating at the Holiday Inn quarantine hotel at Melbourne Airport.

“The previous longest stretch without local cases was 26 days, when there were no cases diagnosed in the reporting cycles between 8pm on November 6 and 8pm on December 2,” NSW Health reported on Sunday.

“While this milestone is pleasing, it does not mean we can drop our guard. Cases are present in other states and are regularly being detected among international travellers arriving from overseas.”

NSW Health is still trying to track down about 350 of the 7000 people who entered NSW after spending time at Melbourne Airport on dates and times of concern, including any location in the airport on February 7 or 8 and terminal 4 at the airport between 4.45am and 2pm on February 9.

“NSW contact tracers have now spoken directly to over 95 per cent of the approximately 7000 people who attended any of the Melbourne Airport terminals from 7 to 9 February, and who subsequently arrived in NSW, to provide the relevant health advice,” the agency said.

“Calls to the remainder are continuing.”

Household contacts of people who visited terminal 4 between the specified times are also being asked to self-isolate until that person receives a negative result.

Two local cases were added to Victoria’s cluster on Sunday, bringing the total to 16.

Lyn Gilbert, a professor and senior researcher at the Marie Bashir Institute for Infectious Diseases and Biosecurity at the University of Sydney, said the chances of the infection spreading to NSW were “quite small” but the state’s success in maintaining no community transmission would depend on contact tracing and luck.

“In NSW, we’ve got a pretty good record of finding people who are contacts but there’s always a possibility that it will spread, it’s a tricky virus,” she said.

“It’s always a combination of a really good system and fast responses and, to some extent, luck. And this is just going to have to continue until everyone’s vaccinated and even then, the vaccine won’t have 100 per cent uptake or effectiveness.”