It is reassuring that New Zealand's first community case of Omicron does not appear to have infected his three housemates, epidemiologist Michael Baker says.
In an Instagram post last night, Briton Robert Etheridge, who goes by the DJ/producer name Dimension, said he received a positive result two days after his 10-day period of isolation.
He has apologised after spending time in Auckland including socialising on Waiheke Island before receiving a negative day nine result.
Professor Baker said he was somewhat relieved after listening to Covid-19 Response Minister Chris Hipkins' briefing about the case this morning.
It included an announcement that the DJ's three housemates with whom he was isolating on Waiheke have tested negative while the result for the fourth housemate has not yet been released.
Prof Baker said he was most concerned to get the answers to two questions: Is the outbreak contained and how did it happen so it could be prevented in the future.
So far as the containment was concerned, the news was "optimistic" because on the face of it an Omicron-positive person socialising in the community for two days, going to a nightclub, dinner and having drinks with neighbours would be a very high risk for transmission.
"It does suggest that this person was perhaps not infectious. The good news is that three out of four of their household contacts or people that person was sharing a house with have been tested and tested negative and we're awaiting the other result.
"All of that is suggesting... they were not infectious while they were out, but again we will just have to await more of those results."
There will need to be more testing of his housemates and other people he has mingled with including anyone he mixed with at indoor gatherings.
"You're basically testing concentric circles out from the case of people who had very close contact and then casual contact and if you find they are all testing negative that's very good news obviously."
He said transmission of earlier variants, such as Delta, occurred at the time cases were at their most infectious and mixed with people in indoor environments.
The other major question was how the DJ got infected.
There were three possibilities, Professor Baker said: The most benign is that it is a historic infection with the PCR test picking up a fragment of the virus that is a residue; the second one is within the MIQ facility; the third is the man has had an extremely long incubation period which would be unusual for the Omicron variant.
"There is pretty good evidence now that it's [the incubation period] reduced from typically five or six days down to about three days now which would suggest that the tail might also be shortened but really there's very little evidence about that at the moment. So it will be very important to find out what happened here."
All three possibilities are on the table and as more results come to light in the next few days it will be decided what is the most likely way the man got infected.
Asked if he was still happy that Auckland was moving from the red traffic light to orange tonight, he described the government's decision as "reasonable at the moment".
RNZ
