Science’s COVID-19 reporting is supported by the Pulitzer Center and the Heising-Simons Foundation.
New Zealand officials and scientists are eying a breach in isolation security as the possible cause of the first cases of community transmission in the country in 102 days. Investigators are exploring several possibilities, but experts believe the alternatives—that the virus was circulating undetected or that it entered the country on a freight shipment—are unlikely.
“We must have had some failure at the border, it’s unlikely there could have been silent transmission for that long,” says Nick Wilson, a public health scientist at University of Otago.
New Zealand has become a model for quick action against the pandemic. The country diagnosed its first COVID-19 case on 26 February; when it became clear by mid-March that there was community transmission, New Zealand Prime Minister Jacinda Ardern laid out a science-driven response that identified four levels of restrictions that would be imposed and relaxed according to circumstances—beginning with a strict lockdown.
Eventually, the country appears to have eliminated domestic transmission completely after less than 1600 confirmed and probable cases and 22 deaths. The last known case of community transmission was identified on 1 May and on 8 June the government moved to Alert Level 1, returning daily life within the country essentially back to normal, though international travel is still restricted. Incoming travelers face government supervised quarantine or isolation for 2 weeks. (Until yesterday, all 22 known active infections were among returning travelers in isolation facilities.)
The cluster of new cases caught the nation by surprise. The government announced yesterday that a person in their 50s living in South Auckland first tested positive for the virus after seeking medical care. Subsequently, three other members of the family tested positive; three others did not have the virus. The index case of the group had no history of overseas travel. All close contacts of the four cases were asked to self-isolate for 14 days; casual contacts will be in self-isolation pending test results.
Today, the Ministry of Health reported finding an additional four probable cases linked to the cases reported on Tuesday. Test results are pending. “It sounds like there has been transmission within a workplace,” Wilson says.
New Zealand scientists doubt the virus has been circulating undetected the past 3 months. “Anybody in hospital with respiratory symptoms gets tested and we’ve had nothing,” says microbiologist Siouxsie Wiles of the University of Auckland. The possibility that the virus hitched a ride into the country on imported chilled or frozen food is being investigated, because one of the infected family members handled such imports at work. Environmental samples are being collected from that workplace. But Wilson considers this route “a remote possibility.” Transmission from contaminated surfaces was the possible mechanism for a few rare cases, he says, but overwhelmingly “it is person-to-person.”
Virus samples from the new cases and from recent travelers are now being sequenced and will be compared to try to identify links. The results should be available tomorrow, Wilson says. In the meantime, the government returned Auckland to Alert Level 3 at noon today, requiring people to stay home except for essential trips. The rest of the country was moved to Alert Level 2, which encourages social distancing but allows gatherings of up to 100 people and domestic travel. The restrictions will be in place for at least 3 days.