Investigators are trying to determine whether New Zealand's mystery Covid-19 outbreak could have been freighted into the country in frozen food or even remain frozen in a cold storage facility for weeks.
One of the people who has tested positive for Covid-19 is an employee at an Americold coolstore in Mt Wellington, one of four people who tested positive on Tuesday.
Americold NZ managing director Richard Winnall told the Herald the man worked in a role where he handled frozen food that was destined for grocery retailers and food service companies.
However, he would have been wearing PPE gear and gloves as part of his handling of those products. He would also have been wearing cold temperature clothing, like a freezer jacket and pants, and possibly a beanie.
The cold storage facility in Mt Wellington has been shut down for testing and cleaning.
While infectious disease experts believe it's more likely the virus was bubbling underneath the surface in Auckland as New Zealand celebrated 102 days virus-free, the prospect it could be "frozen" and remain infectious is troubling.
Director general of health Dr Ashley Bloomfield confirmed on Wednesday that "environmental testing" of a cold storage facility where the person worked was being conducted.
"We do know from studies overseas, that actually, the virus can survive in some refrigerated environments for quite some time," he said.
"We start by looking at all the options and ruling then out, and that's the position we're in at the moment.
"In general the role of surfaces for transmitting the virus has probably been overemphasised in the past.
"There's much more focus now on transmission in indoor environments, and respiratory droplets and aerosols."
To date there appears to be no evidence of virus transmitting through food, freight or food packaging.
"I know that the virus re-emerging in our community has caused alarm and the unknown is scary. That causes anxiety for many of us," Bloomfield said.
"We are working hard to put together the pieces of the puzzle as to how this family got the virus. We are testing all close and casual contacts."
But some experts have raised the possibility the virus could last for months in frozen environments with China blaming frozen food for a second outbreak this year.
Wu Zunyou, Chief Epidemiologist of China's Centre for Diseases Prevention and Control, told Chinese state media this year that the virus can survive on the surface of frozen food for up to three months.
Infectious Diseases physician and microbiologist at Australian National University, Professor Peter Collignon, told news.com.au he was still sceptical that the virus had been "imported" into New Zealand in frozen food.
"But I have always worried when people talk about elimination, it can be so mild in people in their 30s and 40s that it can just be there bubbling away without you knowing," he said.
Prof Collignon said genomic testing which could potentially link the virus to other earlier strains in the community was the key to working out where the virus came from after 100 days Covid free.
"We will have to wait for the genomics. I think it's much more likely it was bubbling under the surface rather than frozen food. But was it from a high prevalence area? It is possible," he said.
"Particularly if its faecal contaminated, because we do know this virus is in faeces.
"Look, my view is one of the places there's the highest risk is abattoirs. It's cold, refrigerated."
- additional reporting news.com.au