Covid 19 coronavirus Delta outbreak: Wastewater testing key to Northland going to level 3 lockdown

Whangārei's main wastewater plant and laboratory, which serves 70,000 people, is being tested for taraces of Covid 19. Photo / Michael Cunningham

Northland's exit from level 4 Covid-19 lockdown on Thursday is hanging on negative regional wastewater surveillance results.

These include from Mangawhai. Other test results are awaited for Kaiwaka, just 38 kilometres north of Auckland's Warkworth where at least one positive Delta case has been confirmed.

Prime Minister Jacinda Ardern said the Government's pending decision to move the region from level 4 lockdown to level 3 hinged on negative results that showed the virus was not present in more than 20 further Northland wastewater tests, in conjunction with several other considerations. Results are due tomorrow.

Other results include from Whangārei's Oakura, Ruakākā, Tutukaka and Waipū, which have only recently been brought into the expanded wastewater surveillance.

Results are also being awaited from Dargaville and Maungaturoto, and the Far North's Whangaroa plant.

Twenty-eight of Northland's 32 reticulated wastewater testing plants are or have been under the spotlight.

Results show the virus has so far not been detected in 18 Northland wastewater treatment plants - Ahipara, Awanui, Hāruru, Hihi, Houhora, Kaeo, Kaikohe, Kaitaia, Kawakawa, Kerikeri, Opononi, Paihia, Rangiputa, Rawene, Russell, Taipā, Whangārei and Whatuwhiwhi.

Covid-19 wastewater surveillance in Whangārei's main Kioereroa Rdtesting plant has been carried out since July.

WDC laboratory manager Lois Howe said the testing was an innovative new tool for detecting the virus in wastewater.

"It provides useful information during an outbreak," Howe said.

Howe said the ultra-sensitive test could detect the distinct RNA strands shed by people carrying the virus. The results were used to alert the Government to the virus' presence in the community, even where cases had not been identified through individual medical tests.