Kiwi scientists are turning to our sewers to flush out Covid-19.
Researchers at ESR are developing a pilot programme to see if the coronavirus can be detected in wastewater.
The approach - called wastewater-based epidemiology - has already been used in New Zealand to study other viruses, and even illegal drug use.
Recent studies have shown that live Sars-Cov-2 – the virus that causes Covid-19 – can be isolated from the faeces and urine of infected people, and can sometimes survive for up to several days after leaving the body.
"If the virus can be detected, we would be in a position to provide information to better understand Covid-19, its prevalence and distribution across the country," ESR's manager for water and biowaste and research and development, Dr Brent Gilpin, told the Herald.
"Globally, research institutes are collaborating on sampling, testing and analysis protocols to provide the best data as quickly and meaningfully as possible."
Scientists found coronavirus in sewage water in the Netherlands, and concluded it likely got there from the faeces of patients.
Dutch researchers said the coronavirus was in samples taken from sewage treatment plants at Amsterdam Schiphol Airport and the village of Kaatsheuvel, which treats waste water from the town where the country's first Covid-19 patient lived.
Their analysis suggested monitoring sewage water was a good way of checking whether viruses such as Sars-Cov-2 was in the population.
The approach could alert scientists and authorities to cases before they were confirmed – or just provide a better picture of community-level infection.
In the UK, researchers at Cranfield University have been developing rapid-testing kits using paper-based devices that could be used at wastewater treatment plants.
"In the case of asymptomatic infections in the community or when people are not sure whether they are infected or not, real-time community sewage detection through paper analytical devices could determine whether there are Covid-19 carriers in an area to enable rapid screening, quarantine and prevention," Cranfield scientist Dr Zhugen Yang said.
"If Covid-19 can be monitored in a community at an early stage, effective intervention can be taken as early as possible to restrict the movements of that local population, working to minimise the pathogen spread and threat to public health."
Otago University epidemiologist Professor Michael Baker saw the approach as "the ultimate form" of pooling samples.
"When you can pool specimens, you might test 20 or 100 samples at once. It's a much more efficient way of testing."
In Wellington and Auckland, ESR and police have used wastewater sampling to search for traces of drugs like methamphetamine, cocaine, heroin, alpha PVP, MDMA and creatinine.
More testing needed
Meanwhile, scientists have called for big improvements in New Zealand's current testing regime.
"We should be testing a lot more people," Otago University public health professor Nick Wilson said.
"Everybody going to a hospital or ED department with a respiratory infection should get tested, not just to improve diagnosis, but to ensure you don't get spread in the healthcare system.
"We need to be testing much more in the community so we can understand what is happening.
"That's why smart sampling of retail workers, like people working in supermarkets or petrol stations, would be ideal, and even give them reassurance that they're not being infected by the public."
Baker said that although testing in hospitals was happening, much more was needed in the wider community, especially among those who met the case definition for infection.
"If we are really thinking about de-escalating our containment measures, we have to do so much more work in that particular group. It's absolutely critical for driving the elimination effort."
This week, the Government announced it would be ramping up testing numbers to 5000 – a 35 per cent increase on its current 3750 daily limit.
Prime Minister Jacinda Ardern has acknowledged the scale of testing was not enough to be able to draw any conclusions about the true extent of community transmission.
"Not only is it too soon to draw conclusions about New Zealand's position as we tackle this global pandemic, we also don't believe we have enough testing to tell us what we need to know," she said this week.
"The more we test, the more it tells us how far our community transmission is, and where it is."