New Zealand officials are scrambling to stop a growing cluster of COVID-19 cases that have prompted health researchers to try to understand how the pandemic coronavirus gained a foothold on the island nation.
Officials on Tuesday announced four cases in one household in Auckland, New Zealand’s largest city. Before that, the country had gone 102 days without local transmission. Throughout the pandemic, New Zealand has been among the most successful countries in the world in responding to and restraining the pandemic coronavirus, relying on rapid and in-depth testing and tracing, as well as on strict social distances and closed orders.
But the new cluster has stumped researchers, who are now investigating all possible ways in which the coronavirus can slide back – including that it arrived on the packaging of shipments of frozen food and infected a worker who unpacked them.
Meanwhile, the cluster has grown since Thursday to at least 17. Auckland has been wrenched back in lockdown measures, and officials have raised the alarm level for the rest of the country, raising some restrictions.
Cold case
The first person in the cluster to test positive was a man in his 50s who was symptomatic for five days. Of the man’s six family contacts, three also tested positive on Tuesday: a child from kindergarten and two adults, according to The New Zealand Herald. One of the adults appears to be a woman in her 20s who works for the lending company Finance Now, and the other is a man who works for a facility operated by Americold, a company in Atlanta, Georgia, that transports goods and stores them at controlled temperatures. Americold operates in the United States, Canada, Australia, and Argentina, as well as New Zealand.
The job of the infected Americold employee was engaged in handling frozen foods that existed for groceries and food service companies. He had been on sick leave for nine days by the time he tested positive, according to Americold NZ Managing Director Richard Winnall, who spoke to the Herald.
Winnall stressed that the chance that the virus would spread to consumers of frozen foods that the infected worker treated was “unreasonable.” He noted that shipments of frozen food come in several layers of packaging, and the infected worker probably did not touch the packaging layers that would eventually be touched by consumers or employees of food services. Winnall also noted that the infected worker would have personal protective equipment, including gloves, and reduced the chance of transmitting infectious virus to food packages.
“Look at all the options”
Still, without a clear explanation of how the employee and his family were infected in the first place, health researchers are investigating the possibility that he was infected by virus particles that were sent on the frozen goods. Health officials and health experts suggest this seems likely, but not impossible. There have been several reports from China about health officials detecting genetic material of the coronavirus, SARS-CoV-2, on frozen goods. In an example this week, authorities in the eastern Chinese port city of Yantai have discovered traces of the virus on imported frozen seabirds. The genetic traces suggest infection with the coronavirus, but not necessarily highly infected virus particles.
New Zealand Director General of Health Ashley Bloomfield said this week that surfaces at the Americold facility will be inspected to see if frozen cargo or anything else may have been the source of the new infections. “We know from studies from abroad that the virus can actually survive a long cool time in cool environments,” he said. For the research, “we start by looking at all the options and then decide out, and that is the position where we are at the moment.”
Not likely, but not impossible
The possibility that SARS-CoV-2 may survive on shipping frozen goods is not wild. Studies have suggested that some virus particles can remain infected for three days on plastic surfaces at room temperature. And the virus is more stable at lower temperatures, like those in a cold store.
This means the virus could remain viable for even longer, infectious disease and food safety researcher Hamada Aboubakr tells 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 in various conditions.
Aboubakr claims it is theoretically possible that SARS-CoV-2 could spread through contaminated food or food packaging. In addition to cold survival, there are early laboratory data that suggest that the virus can survive in highly acidic conditions, similar to the environment of the human stomach. But 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 have confirmed such link.
The point is reiterated 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 researchers in New Zealand need a lot more data and information to assess the risk of cargo proliferation and pin the new cases to contaminated packages.
Bad luck
Researchers of infectious disease Amandine Gamble agree. Gamble is a researcher at the University of California, Los Angeles, who recently led a study on treatments to inactivate SARS-CoV-2. “It is very plausible that SARS-CoV-2 can remain viable on frozen surfaces for several days,” she tells Ars. “However, it is not clear whether the virus can be easily transmitted through contaminated surfaces.”
There are many unknowns about the situation and basic transportation of SARS-CoV-2, she adds. For example, we do not know how many viral particles are sufficient to trigger an infection. But, she says, by running the scenario in which a worker would be infected by an infected package, “it may seem like an unlikely route of transmission.”
Let’s imagine in such a scenario that an infected person coughs on a frozen bag, and she removes X number of viral particles on the bag, she says. Several people can then handle the bag, and the bag is likely in contact with other bags and containers, all of which cause some of the particles to rub. Then during transmission some viruses are naturally degraded – even if it is a slower rate then would be observed at warmer temperatures. Then a worker touches the bag, transferring some virus particles from the bag to their hands. The worker touches her face, transfers even fewer particles from her hands to her face, and then simply inhales some of these particles. And only some of them will encounter even sensitive cells. Eventually, the worker would encounter a much, much smaller number of virus particles than the first X quantity on the bag.
Being “purely speculative”, such a transfer power be possible, says Gamble, if there was a very large number of virus particles on a bag to begin with – through a large, direct snow or contamination of several infected people – and the bag was shipped quickly, did not have much treatment, and a receiving worker had no protective equipment and quickly touched her nose. “It’s unlikely that all of these events are coordinated – though not impossible,” she says. “But it would be very bad luck.”
As far as consumers are concerned, Gamble suggests that if frozen food were a major risk, it is unlikely that New Zealand could have gone more than 100 days without seeing other cases. For anyone who is worried about getting SARS-CoV-2 from frozen foods, they are advised to make sure you wash your hands and regular surfaces frequently.
Cluster continues
While the source of the cluster remains unknown, health officials on Thursday announced 13 additional cases. All of these cases are in some way linked to the original four, including three other Americold employees and seven of their family members. An employee at Finance Now and a family member of that employee also tested positive. Finally, there was one community issue linked to the cluster.
One of the new cases is a student at a local grammar school, and another had recently visited a nursing home. Officials drive to identify, test and quarantine the number of types of contacts.
According to a new report from the Herald, genetic testing suggests that the new cluster of cases is not linked to previous cases isolated in quarantine facilities. Deputy Prime Minister Winston Peters has suggested that the cluster may 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. .
