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Covid-19 Wastewater Testing Results

ESR undertakes testing of wastewater throughout New Zealand on behalf of the Ministry for Health for the presence of SARS CoV-2, the virus which causes COVID-19.

The results of ESR’s testing play an important part of New Zealand’s response to COVID-19, along with community testing and genome sequencing. This early warning can lead to increased local vigilance and clinical testing and allow health authorities to target public health advice to prevent transmission.

About Wastewater Testing Results

Currently, ESR conducts testing of samples collected from locations around New Zealand. When there are known cases of COVID-19 in the community ESR may increase the number of tests being undertaken, while, when the risk is considered to be lower, it may reduce the number of sites being sampled.

The frequency of sampling will vary depending on the local population, access to wasterwater collection points and risk factors.

Each week the results of wastewater samples collected by the Saturday of each week are presented from throughout Aotearoa New Zealand.

Sampling methods

The preferred option for wastewater sampling is called the ‘automatic composite sample’. This is where a pump automatically collects a small volume of wastewater every 15 minutes over 24 hours. These are available in some wastewater treatment plants. When composite samples are not available, ‘grab sampling’ may be used which can range from a sample taken at a single point in time, to 3 samples taken over 30 minutes, to samples collected over a day.

What does a ‘detection’ of SARS-CoV-2 mean?

A positive detection in the wastewater indicates that at least one person has been shedding SARS-CoV-2 into the wastewater in the 24 hours before each sample was collected. Just as a negative finding does not necessarily guarantee an absence of COVID-19 in the community, it should be noted that a positive finding does not necessarily mean that active COVID-19 infections are present in the community. A positive detection in the wastewater could also be due to a case in a managed isolation facility and/or a non-infectious historical case or a non-infectious recently recovered case who is still shedding low levels of SARS-CoV-2.

What should I do if SARS-CoV-2 has been detected in wastewater in my area?

Any detections highlight the importance of getting tested if you have symptoms of COVID-19 or have been in known places of interest.

Why isn't my community included in the wastewater surveillance program?

Locations for sample collection have been chosen based on a range of factors including to represent larger population centres, popular holiday towns and risk factors. Additional testing locations may be added in the future.

Which wastewater treatment plant services my community?

If you are unsure which wastewater treatment plant or facility services your suburb, you should contact your local council.

For more information check out ESR’s wastewater factsheet(external link)