Enlarge /. WELLINGTON, NEW ZEALAND – AUGUST 13: Prime Minister Jacinda Ardern speaks to the media at a COVID-19 briefing on August 13, 2020. COVID-19 restrictions were reintroduced across New Zealand after four new COVID-19 cases were diagnosed in Auckland. Auckland has been put on lockdown level 3 for three days starting Wednesday, August 12th. All residents are required to work from home unless they are a vital workforce and all schools and daycare are closed. The rest of New Zealand has returned to level 2 restrictions. The new cases all belong to the same family and health officials are working to pinpoint the source of the infection.
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New Zealand officials are scrambling to stop a growing number of COVID-19 cases that baffled health researchers to understand how the pandemic coronavirus has regained a foothold on the island nation.
Officials on Tuesday announced four cases in a family in Auckland, New Zealand's largest city. Previously, the country had gone 102 days with no local broadcast. Throughout the pandemic, New Zealand has been one of the most successful countries in the world when it comes to responding to and holding back the pandemic coronavirus. It included quick and thorough testing and tracking, as well as strict instructions on social distancing and banning.
But the new cluster has baffled investigators, who are now investigating all possible ways the coronavirus may have re-entered – including the fact that it landed on the packaging of frozen food shipments and infected a worker who was unpacking them.
The cluster has now grown to at least 17 from Thursday. Auckland has been pushed back into lockdown measures, and officials have raised the alert level for the rest of the country and reintroduced some restrictions.
The first person in the cluster to test positive was a man in his fifties who had been symptomatic for five days. Of the man's six family contacts, three tested positive on Tuesday: one preschooler and two adults, according to The New Zealand Herald. One of the adults appears to be a woman in her twenties who works at Finance Now lending firm, and the other is a man who works at a facility operated by Americold, an Atlanta, Georgia-based company that makes merchandise controlled controlled and stored temperatures. Americold operates in the United States, Canada, Australia and Argentina, and New Zealand.
The infected Americold employee's job was to handle frozen foods for grocery stores and food service providers. According to Richard Winnall, managing director of Americold NZ, who spoke to the Herald, he was on sick leave for nine days when he tested positive.
Winnall stressed that the likelihood that the frozen food virus that the infected employee was handling would spread to consumers was "unlikely". He noted that frozen food deliveries are in multiple layers of packaging and the infected employee likely did not touch the layers of packaging that will ultimately be touched by consumers or grocery workers. Winnall also noted that the infected employee would have worn personal protective equipment, including gloves, which reduced the likelihood of them transmitting infectious virus onto food packaging.
"View all options"
Without getting a clear explanation of how the employee and his family got infected in the first place, health researchers are investigating the possibility that he was infected with virus particles that were shipped on the frozen products. Health officials and experts suggest that this seems unlikely but not impossible. There are several reports from China that health officials have detected genetic material from the coronavirus SARS-CoV-2 on frozen foods. In an example this week, authorities in the east China port city of Yantai discovered traces of the virus on imported frozen seafood. The genetic traces indicate contamination with the coronavirus, but not necessarily whole infectious virus particles.
New Zealand's director general of health Ashley Bloomfield said this week that surfaces at the Americold facility are being tested to see if frozen cargo or something else could have been the cause of the new infections. "We know from studies overseas that the virus can actually survive for some time in some refrigerated environments," he said. For the investigation, "we first examine all options and then rule them out, and that is where we are now."
Unlikely, but not impossible
The possibility that SARS-CoV-2 could survive in the delivery of frozen goods is not small. Studies have shown that some virus particles can remain infectious on plastic surfaces for three days at plastic temperature. And the virus is more stable at lower temperatures than in a cold store.
That means the virus could stay viable for even longer, Infectious Disease and Food Safety researcher Hamada Aboubakr told Ars.Aboubakr is a researcher at the University of Minnesota and was recently the first author of a scientific review on the stability of SARS-CoV 2 on surfaces under different conditions.
Aboubakr suggests that it is theoretically possible for SARS-CoV-2 to spread through contaminated food or food packaging. In addition to survival in the cold, there is early laboratory data to suggest that the virus can survive in highly acidic conditions, similar to the environment around the human stomach. However, he notes that experts are skeptical about this. Overall, he says, "there is no sharp answer" to the risk of food and food packaging, as no studies like Link have confirmed.
The point is confirmed by the World Health Organization, which states that "there is currently no evidence that humans can catch COVID-19 from food or food packaging".
Aboubakr says investigators in New Zealand will need a lot more data and information to assess the risk of cargo spillage and to attach the new cases to contaminated packages.
Amandine Gamble, an infectious disease researcher, agrees. Gamble is a researcher at the University of California at Los Angeles who recently conducted a study of treatments to inactivate SARS-CoV-2. "It is very plausible that SARS-CoV-2 can remain viable for several days on frozen surfaces," she tells Ars. "However, it is not clear whether the virus can be easily transmitted via contaminated surfaces."
There are many unknowns about the situation and basic transmission of SARS-CoV-2, she adds. For example, we don't know how many virus particles are enough to trigger an infection. However, she says as she goes through the scenario in which a worker is infected by a contaminated package, "it seems like an unlikely route of transmission".
In such a scenario, imagine an infected person coughing on a frozen bag and excreting x virus particles on the bag, she says. Several people can then handle the bag and the bag is likely to come into contact with other bags and containers, causing some of the particles to rub off. A virus is then broken down naturally during shipping – even if it is slower than warmer temperatures. Then a worker touches the bag and transfers some virus particles from the bag to their hands. The worker touches his face, transfers even fewer particles from his hands to his face, and then inhales only some of those particles. And only some of them will even encounter susceptible cells. In the end, the worker would encounter a much, much lower number of virus particles than the initial amount of X on the bag.
As "purely speculative", such a transmission could be possible, says Gamble, if a very large number of virus particles were initially on a bag – from a large, direct sneeze or contamination from several infected people – and the bag was shipped quickly, didn't have a lot of handling, and one receiving worker had no protective gear and quickly touched her nose. "It is unlikely that all of these events would be coordinated – although it is not impossible," she says. "But it would be very bad luck."
As for consumers, Gamble suggests that if frozen foods had been a major risk, New Zealand is unlikely to have been able to go more than 100 days without other cases. For anyone concerned about getting SARS-CoV-2 from frozen food, she recommends washing hands and common surfaces frequently.
While the cluster's source remains unknown, health officials announced 13 more cases on Thursday. All of these cases are in some way related to the original four, including three other Americold employees and seven of their family members. A Finance Now employee and a family member of that employee also tested positive. Most recently there was a community case that was linked to the cluster.
One of the new cases is a student at a local high school and another had recently attended a nursing home. Officials are trying to identify, test, and quarantine the growing number of contacts.
According to a new report from the Herald, genetic testing suggests the new clump of cases is not linked to previous cases in quarantine facilities. Deputy Prime Minister Winston Peters has suggested the cluster could be the result of a breach of the country's quarantine system, but a spokesman for the Prime Minister's Office said there was no evidence of such a breach.