ESR have launched an interactive map and dashboard(external link) of COVID-19 wastewater sampling locations throughout New Zealand.
The weekly report highlights sites tested since 11 September. It is updated every Wednesday to include the results of testing for the week up to the preceding Saturday. The latest dashboard includes the results of all tests taken up to and including Saturday, 2 October.
Dr Joanne Hewitt, Senior Scientist at ESR says the dashboard will provide New Zealanders with information on the testing of wastewater in their region, however the most up to date information on any detection of COVID-19 in communities will continue to be released by the Ministry of Health.
“ESR undertakes testing of wastewater throughout New Zealand on behalf of the Ministry for Health. The information can provide an early warning for increased local vigilance and clinical testing and help inform the public health response, says Dr Hewitt.
“Since the beginning of the current delta outbreak, wastewater testing has increased from 26 sites to more than 170 sites, with the number of samples analysed shooting up from 40 per week to well over 300 at the peak of testing.
“It has been a real team efforts and our dedicated team of scientists at ESR couldn’t do it without the support of samplers, Councils and couriers throughout Aotearoa,” says Dr Hewitt.
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 wastewater collection points and risk factors.
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.
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.