Source: ESR
ESR’s testing of wastewater samples collected on Monday 16 August and Tuesday 17 August from four Auckland wastewater treatment plants have returned positive results for COVID-19. The sites covered the North Shore, Western and Eastern Auckland, while sampling from Tuesday 17 August of the Waitakere area of Auckland also coming back positive. The most recent sampling from South Auckland was negative for COVID-19.
Sampling undertaken on Monday and Tuesday at Mt Maunganui, Tauranga, Hamilton, Rotorua, Gisborne, Taupo, New Plymouth, Napier, Porirua, Hutt Valley, Wellington, Nelson, Christchurch, Queenstown and Invercargill have all come back negative.
Further results are expected late today (19 August) from samples taken around the Auckland region with additional results expected tomorrow from other Auckland sites, as well as the results of samples taken from several locations including in the Coromandel and Thames district.
Describing the testing involved, ESR Chief Scientist, Brett Cowan said “the process to find COVID-19 in wastewater makes looking for a needle in a haystack look easy!”
“There’s about a billion litres of sewage every day in New Zealand. If we were to put the coronavirus on the head of a pin there might be a million, million viruses on that pin. ESR’s challenge is to look through a billion litres to find a virus that small.”
ESR’s laboratories receive one litre samples from the wastewater treatment plants and then laboratory staff get work to process them as quickly as possible. Staff take up to 500 ml from those samples and store the rest. As viruses can be attached to the solids and be in the water, methods that will recover viruses from both parts, so as not to lose any virus, are used. The water is then concentrated down to about half a teaspoon leaving the virus behind before being processed to determine if it is positive or negative for the virus using a similar method to the regular testing for the virus of someone’s COVID test swab.
Cowan said wastewater testing was “another important tool in tool kit.”
“We have testing of individuals, our contact tracing and our wastewater testing; these three surveillance tools work together for us as we attempt to identify COVID-19 in the community.”
