They could be because of recently recovered cases continuing to “shed” the virus, the ministry said yesterday.
“Wastewater testing is very sensitive and can pick up if they’ve had the virus previously,” Deputy Prime Minister Grant Robertson told TVNZ’s Q+A this morning.
“That’s still regarded as the most likely scenario at play here but we want to cover off all our bases.”
Update on infected mariners
Six crew members from the Viking Bay vessel, docked at Queens Wharf in Wellington, have returned to the boat from managed isolation. There are now 10 crew members in quarantine on board, up from four yesterday. Ten remain in MIQ onshore in Wellington.
All crew onboard the Playa Zahara have recovered and are back on board the ship docked in Lyttelton. One crew member has returned home.
There have been no changes to cases aboard the Mattina. Fifteen positive cases remain on the vessel. Five crew who tested negative have been transferred to MIQ onshore.
Yesterday's Covid cases
Three positive cases and two historical cases were reported in managed isolation facilities yesterday.
Among them were recent returnees from Mexico via the United States, Russia via Singapore, the United Kingdom via Qatar, and the Philippines via Australia.
New South Wales has recorded 141 new locally acquired Covid-19 cases today and two more deaths from the virus.
Thirty-eight of today’s community cases were infectious while in the community.
Yesterday, 163 new cases were recorded. Forty-five were infectious while in the community.
Victoria has recorded 11 new Covid-19 cases overnight. However, all cases are linked to the current outbreaks. This brings the state’s number of active cases to 179.
All positive cases were in quarantine throughout their entire infectious period.
Robertson said the transtasman travel bubble would only re-open if community transmission of the Delta variant was “contained”.
It was paused for at least eight weeks on Friday, giving New Zealanders seven days to return home.