Still Unknown: Where Did New Zealand Outbreak Originate?

New Zealand's mysterious COVID-19 outbreak stands at 37 cases as of Saturday, the Guardian reports. What's still not clear, reports NPR: Where those cases stem from. Authorities continue to investigate where the family of four who initially tested positive Tuesday—the country's first cases from community spread in 102 days—got infected. Authorities are investigating several theories, including, per the AP, the possibility that workers at the port or on a freight ship somehow spread the coronavirus despite those sites having physical distancing requirements in place and ship workers being barred from coming ashore. Other possibilities:

• Several of those infected in the new cluster work at an Americold cool storage facility in Auckland, and officials are swabbing surfaces there to probe the possibility that the virus survived on cold or frozen food shipped from overseas and then infected employees. But a food microbiologist says that while that's "theoretically possible, ... all indications are that it is not very likely." New Zealand's food safety authority said Thursday that the risk of transmission via food or packaging is "negligible."
• Human-to-human transmission is still considered the vastly most likely source, and another theory involves the idea that the virus has been circulating in the country all this time, but at such a low level that it took until now for a host to get sick enough to develop symptoms and get tested. But the genomic data for the strain of the virus involved suggests it's different from those that circulated in New Zealand earlier in the year. "It appears to be new to New Zealand," Prime Minister Jacinda Ardern says.
• Similarly, the strain doesn't match samples of positive cases from travelers entering New Zealand, so it also seems unlikely that one of them transmitted the virus to an airport worker or employee of a quarantine facility, who then transmitted it to the current cluster.

What is clear: Most of the cases, with one exception, can be linked to the original family of four, and all of the cases except two are in Auckland. Those two are in Tokoroa, and authorities believe the virus is unlikely to spread further there. Auckland's lockdown was on Friday extended for 12 more days as officials continue to work to stamp out the outbreak. (More coronavirus stories.)