Wastewater testing is being carried out by ESR in South Auckland and Taranaki to see whether the Covid-19 virus has spread further in the community.
ESR researchers test wastewater samples from managed isolation facilities. Photo: RNZ / Dom Thomas
Testing in the area as recent as 10 February found no signs of Covid-19 in the water.
ESR chief scientist Brett Cowan told Morning Report the company had been testing sewage from managed isolation hotels alongside communities without MIQ facilties since November.
Covid-19: Wastewater testing underway in Auckland, Taranaki
"We previously tested less frequently but in our cooperation with the Ministry of Health, ESR's rolling out daily testing in Auckland and New Plymouth to watch this on a much finer time scale," he said.
The lack of the virus found in sewage in the area thus far could be promising, looking at the results of prior testing around managed isolation facilities.
"We've done testing right outside the Jet Park hotel and it won't come as a surprise that we found we were able to detect the virus in sewerage there," he said.
"But then we tested downstream after perhaps 130,000 had flushed their toilets into that sewerage pipe and we found that if perhaps three or four or five people at Jet Park were positive, we were still able to detect the virus after 130,000 other people had added to that sewage stream."
Results from yesterday's testing were not yet available, but Cowan said they were expecting the earliest results to be ready tomorrow.
A number of countries around the world were also using wastewater testing and it represented another tool in New Zealand's surveillence toolkit, he said.
"If we imagine we were searching for sailors lost at sea we might send out boats - and that's like the nasal swab. We might add aircraft, which is our community testing, identified by contact tracing. But testing sewerage is kind of like having a satellite, where we can see a huge amount of ocean. And whilst we might not be able to see it with the resolution of an aircraft or a boat, we're able to see enough to direct those aircraft or boats to an area of interest."
Collection of sewage was performed by an automatic device which takes a small sample from the wastewater system every 10 minutes.
"They're all added up over 24 hours and about a litre of sewage is sent to the laboratory for analysis," Cowan said. "The first thing we do is we concentrate that litre down to about a tablespoon, we extract the RNA from the virus and then we use a very similar process, PCR, which is used for the nasal swabs, to identify the RNA that's specific to the Covid virus."
Survellience testing around the country had been performed in around six or seven sites over the last few months, but Cowan said there had been no results so far that had prompted them to look more closely at a particular area.