Wastewater tests for COVID launching in bid to spot outbreaks early

Doug Hendrie

10/09/2020 12:55:40 PM

A pioneering surveillance program is already proving its worth in finding virus fragments – and alerting authorities to potential cases.

Retrieving wastewater sample
Wastewater testing should give authorities the ability to notice hotspots early and bring in public health measures accordingly.

Every week, workers are taking samples of wastewater in sewage treatment plants and pumping stations around Australia. These vials will be analysed for traces of the coronavirus that causes COVID-19.
The ultimate goal of the Water Research Australia project ColoSSoS – Collaboration on Sewage Surveillance of SARS-COV-2 – is to accurately detect the presence of the virus in sewage and, ideally, to provide early warning well before people notice symptoms and come in for testing.
People start shedding the virus as early as two days after becoming infected.
For the cost of around $500 per sample, wastewater testing should give authorities the ability to notice hotspots early and bring in public health measures accordingly.
Wastewater testing is most useful when the virus is present at low levels and not self-evident from clinical testing in those same areas, holding out the promise of new ways of keeping the virus as low as possible, in conjunction with tracing, testing and other surveillance methods.
The tests have now been shown to detect the virus even at very low levels; but to help better inform decision-makers, the results gathered to date need to be analysed so the methods can be calibrated in areas of high, medium, low and zero COVID presence.
Victorian Health Minister Jenny Mikakos said in a statement that wastewater testing ‘may be able to give us early warning that coronavirus is in a community and the head start we need for early detection and preventive action’.
Early testing has found traces of the virus in wastewater in regional towns like Apollo Bay in Victoria, Airlie Beach in Queensland and Perisher ski resort in NSW.
The project is most advanced in Victoria, with up to 300 samples a week tested from 25 sites across Victoria. South Australia has also found evidence of the virus in its testing through the project. Other states where the coronavirus is currently present such as New South Wales are at a pilot stage.
Queensland, however, has launched its own pilot standalone program with the University of Queensland and the CSIRO.
Project manager and microbiologist Dr Dan Deere told newsGP the test is proven to work, with thousands of samples now taken in Australia and data analysis and interpretation under way. There are similar programs occurring globally. 
‘Sewage testing is very efficient; if you have one infected person shedding the virus amongst thousands, the test should be able to pick that up in one sample,’ he said.
‘You would primarily use it when there are low case numbers or no cases.
‘Our goal is to provide data to COVID-control taskforces at a state level and share the data nationally. It will be used as extra evidence to sit alongside swab testing, antibody testing, data from genotyping to find out if cases are linked, and contact tracing,’ he said.
The test could also give regional towns – where sewage goes through a single treatment plant – the ability to show the virus was not currently present above levels of detection. In major cities, testing has to be done both at large sewage treatment plants as well as suburb-level pumping stations, in order to get more granular detail.
But before it can start feeding usable data into state and federal COVID-control taskforces, the test has to be validated for sensitivity (how often a test correctly finds a result is positive) and specificity (how often a test correctly comes back negative for samples that do not have the virus).
Early indications are encouraging, Dr Deere said.
‘The test does all the things we want it to do. We don’t get high rates of false positives or false negatives, so it’s a useful test. But we have yet to show that systematically.
‘Wastewater testing could be one additional input to a decision to lock down an area, or release an area from lockdown. Testing could be part of the input in deciding which countries can travel to each other and which ones can’t.’

‘If you have one infected person shedding the virus amongst thousands, the test should be able to pick that up’: microbiologist Dr Dan Deere said of the wastewater testing project. 

The project is now moving to a final analysis stage. Medical epidemiologists are crunching the data and comparing virus prevalence in wastewater to cases found through clinical swabs done in specific communities.
So far, the signs are good: ‘We don’t routinely find the virus in cities with no cases [from clinical testing] and vice versa,’ he said. 
Dr Deere said the test picks up non-infectious viral fragments left after the virus breaks down.
‘One of the questions we’re looking at is how long after we lose infectivity do we still see a signal [from the test]? Researchers in the US have found it’s a surprisingly short-lived signal after the virus stops being clinically relevant. We don’t think it will be weeks or months – more like days, which is much shorter than it could have been,’ he said. 
‘We are trying as far as possible to align this with medical approaches to testing and diagnostics, in line with clinical and pathology testing. This program is largely driven by and funded by health departments – it’s very much a health-led, health-aligned program.’
The ColoSSoS project is a collaboration between Australian states and New Zealand, with health departments, water utilities, laboratories and experts all involved.
The Netherlands are the world leaders in sewage surveillance for the virus that causes COVID, with a public dashboard showing the current rate of virus detected in sewage water from 80 locations around the nation.
Wastewater testing has proven its worth in the decades-long global fight to eradicate the poliovirus, with testing required even in polio-free nations like Australia. 
‘Sewage testing has been going on behind the scenes for decades for viruses like adenoviruses, the bacterium that causes typhoid or even the first SARS coronavirus. This is nothing new – we just need to change the target,’ Dr Deere said.
Early fears about the safety of sewage workers – or of people swimming in beaches near where treated sewage is released – have eased.
‘The virus is very fragile in sewage – and that’s not true of polio, for instance. Once it’s in water or sewage, for practical purposes, all that’s left after a day or two is just the fragments such as the RNA. So it’s not seen as a waterborne virus. If it gets into disinfected swimming pool water, the virus is dead within seconds due to chlorine.’ 
Water Research Australia CEO Karen Rouse said that the early stages of the project confirm sewage testing is ‘feasible and promising’ as a tool to complement measures such as clinical testing.
‘The project has been successfully initiated with rapid development of sampling, processing and laboratory testing methods for sewage surveillance. It is continuing to ensure initial detection methods used across the nation are robust, sensitive, specific and comparable, while also identifying any improvements that can deliver greater efficiency and ease of implementation.’
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