How an Auckland Rydges Hotel worker contracted COVID-19 remains a "mystery", Dr Ashley Bloomfield says.
The hotel is being used as a managed isolation facility, and the infected staff member was employed as a maintenance worker. His infection was confirmed on Tuesday.
His case isn't linked to the Auckland community cluster. Instead, the same genome sequencing of the virus in this man has also been identified in samples from a returnee who arrived from the United States. This person stayed at the Rydges Hotel on arrival to New Zealand in July and tested positive for COVID-19.
The Director-General of Health says the worker was tested on August 13, and as soon as the result came back positive, he was put into self-isolation and his close contacts were identified.
"This is someone who works as a maintenance worker for the hotel, so he doesn't have direct interaction with any of the guests. So once again, a little bit of a mystery here, one that we will be investigating fully to find out," Dr Bloomfied said on Tuesday.
The infected worker showed mild symptoms two days before his test which he attributed to a pre-existing condition.
Dr Bloomfield says there are two possibilities for how the employee contracted the virus. The first is through human-to-human transmission and the second is through environmental contamination where the virus lives on a surface.
"But I can say that when the maintenance workers enter any room that someone positive might've been in, they do have appropriate PPE," he says.
The Ministry of Health says after reviewing CCTV footage and swipe card movements at the Rydges Hotel, no link has been found so far between the two cases. The room the US returnee was staying in before they were shifted over to the Auckland quarantine facility hasn't been occupied since their stay. The room underwent "hospital-grade cleaning" after they left.
Professor Michael Plank from Te Pūnaha Matatini and the University of Canterbury says since the hotel worker didn't have face-to-face contact with guests, it suggests transmission may have happened via a contaminated surface or another border worker that wasn't detected to have the virus.
"This underscores the importance of regular testing of everyone working at the border or quarantine facilities. If the worker is the index case for this outbreak, there is a good chance we have caught it before it can cause a major new cluster. But we won't know for sure until the contact tracing investigation is complete," he said in a statement.
Epidemiologist Dr Siouxsie Wiles also says this case shows the importance of regularly testing border and managed isolation and quarantine facility workers.
"The latest information shows just how important genome sequencing can be in helping to identify potential sources of COVID-19 transmission in countries like New Zealand which are managing the pandemic well," she says.
Health Minister Chris Hipkins says there are "very extensive" protective measures in place at managed isolation and quarantine facilities.
"It does show that this is a highly contagious virus that is easy to get and we're doing everything we can to put protective measures in place."
But he says there's "no such thing" as a 100 percent guarantee someone won't become infected, even if the "very best" measures are in place.