The testing blitz comes after ESR detected a positive result for Covid-19 in New Plymouth’s wastewater this week. A follow-up sewage sample also returned a positive result on Friday night.
The Covid-19 spotlight is on Taranaki, with health officials urging anyone with symptoms of the virus, or any people there who have recently returned from Australia to be tested.
The testing blitz comes after ESR detected a positive result for Covid-19 in New Plymouth’s wastewater this week. A follow-up sewage sample also returned a positive result on Friday night.
In a statement on Saturday, the Ministry of Health said that the two positive wastewater results detected in Taranaki could be due to recently recovered cases continuing to shed the virus, or could signal undetected cases in the community.
The Institute of Environmental Science and Research (ESR) undertakes regular wastewater testing across the country as an additional surveillance tool for Covid-19.
What is wastewater testing?
Speaking to Stuff, professor Nick Wilson, from the University of Otago Wellington’s Department of Public Health, said wastewater testing is being used widely around the world and is “proving to be an additional, useful surveillance tool”.
Wastewater testing first started here in April 2020, with the aim of giving an early warning of outbreaks or an additional surveillance tool.
The science has been developed since then with a test in November 2020, and ESR now does regular wastewater testing across multiple sites in New Zealand, including in the country’s major cities.
The samples are processed in ESR’s laboratory in Wellington, and checked for accuracy.
How are virus fragments detected?
Wastewater testing is rather sensitive and can detect virus fragments, Wilson said. People previously infected with the virus who have been through MIQ and are no longer contagious, can still have virus fragments in their bodies.
Once they’ve been to the toilet, it’s possible samples taken from a city’s wastewater can detect these fragments, which Wilson said is possibly what’s happening in Taranaki.
“This has in fact happened a number of times in the past in New Zealand,” he said. Wilson added that it means the surveillance system is working as it should.
Why testing is so important
In its release on Saturday, the ministry said the positive wastewater results could be either from recently recovered cases continuing to shed the virus, or it could signal undetected cases in the community.
In order to determine whether there are any undetected cases, the ministry is recommending all symptomatic people in Taranaki get tested, as well as all recent arrivals from Australia who are in Taranaki – even if those new arrivals do not have symptoms.
Testing capacity has been increased in New Plymouth to support potential demand.
“There is a chance, whenever you get a positive result, that this does reflect community transmission, and that is why it’s very sensible for the Ministry of Health to encourage people in Taranaki, if they have symptoms, to get tested,” Wilson said.
“But based on past experience and the fact that this is not in a place where we would normally expect a outbreak to start in New Zealand – because there’s no MIQ facilities or there’s no international airport – this is very likely to represent just the non-infectious virus fragments.”
Wilson said it was good to be cautious and for symptomatic people in Taranaki to get a test to help rule out the chance that this is a true infection.
Further wastewater sampling was carried out on Saturday and those results were expected back on Monday.
Although the mariners aboard the Playa Zahara and Viking Bay vessels recently docked at Port Taranaki, in New Plymouth, the dates of their brief visits, and the activity of the crew do not appear to be a factor in the wastewater detections, the ministry said.
Additional testing is being carried out for a small number of port workers and nurses, who have been in possible contact with the mariners. All test results to date are negative with two results pending.
Advice for those in Taranaki
Anyone with symptoms consistent with Covid-19 should call Healthline (0800 358 5453) for advice on getting a test.
Anyone in Taranaki who has symptoms is urged to get tested, as well as any symptomatic people who have visited the region recently.
Originally published at Stuff