Wastewater testing may provide early warning of coronavirus (COVID-19)

Key points

  • Testing of wastewater can show if SARS-CoV-2 – the virus that causes coronavirus (COVID-19) – is present in a local community.
  • Victoria has joined other Australian states and territories and New Zealand in collaborative research that will help us detect coronavirus (COVID-19) viral fragments in wastewater systems and use testing results with other health data as part of our response.
  • People who have or have recently had coronavirus (COVID-19) may shed fragments of the virus. These fragments can enter wastewater through bowls, sinks and drains. This viral shedding may come from different sources such as used tissues, off hands and skin, or in stools. This may last for a number of weeks beyond a person’s infectious period.
  • Samples of wastewater are collected from treatment plants and in the network, both in metropolitan and regional locations. These samples are analysed for fragments of coronavirus (COVID-19).
  • If fragments of coronavirus (COVID-19) are detected in the wastewater of an area where there have not been recent positive cases, local communities can be more vigilant, increase clinical testing, and help health authorities to target public health advice to minimise transmission.
Your questions answered

Why are you testing wastewater?

Wastewater monitoring can give a snapshot of the possible presence of SARS-CoV-2 - the virus that causes coronavirus (COVID-19) - in a local area.

Victoria has joined other Australian states and territories and New Zealand in collaborative research. This will help us to understand the occurrence of coronavirus (COVID-19) viral fragments in wastewater systems and use testing results with other health data in our response efforts.

Coordinated by Water Research Australia, the ColoSSoS (Collaboration on Sewage Surveillance of SARS-COV-2) project brings together health departments, water utilities, laboratories and researchers to share advances in this rapidly evolving field.

How do traces of coronavirus (COVID-19) get into wastewater?

People who have had coronavirus (COVID-19) may shed the virus or virus fragments on used tissues, off their hands and skin when washing, and in their stool.

Over time the virus breaks down and small pieces of the virus (called ‘viral fragments’) can enter wastewater through bowls, sinks and drains, and then travel through the sewer network.

While viral fragments may indicate that people within a community have or have recently had coronavirus (COVID-19), people can still shed the virus for several weeks, well beyond their infectious period.

How are wastewater samples taken and tested?

Samples of wastewater are collected every week from wastewater treatment plants and in the network at several metropolitan and regional locations.

The samples are analysed for fragments of coronavirus (COVID-19).

These tests detect the specific virus associated with coronavirus (COVID-19) and distinguish it from other types of coronavirus.

Where are wastewater samples taken?

Wastewater samples are taken from more than 30 sites across Victoria. In metropolitan areas, samples are taken at the large Eastern and Western treatment plants and several locations throughout the metropolitan sewerage system. In regional Victoria, samples are taken at sewage treatment plants including Ararat, Ballarat, Benalla, Bendigo, Mildura, Moe, Shepparton, Swan Hill, Traralgon, Wangaratta, Warragul, Wodonga and Wonthaggi, and at 11 sites in the Colac-Otway, Surf Coast and Greater Geelong areas.

What has your wastewater testing found?

Since late August 2020, wastewater samples have been collected and tested from locations across the metropolitan and regional sewer network.

Traces of coronavirus (COVID-19) have been found in samples from many metropolitan and regional locations. This is expected, because there were known active or recent cases in those locations.

Samples taken in September 2020 in the small coastal community of Apollo Bay were found to contain fragments of coronavirus (COVID-19) in the absence of any known cases in the town. This led to repeat wastewater testing, and public messaging for individual testing coupled with a boost to local testing services.

What happens when coronavirus (COVID-19) is detected?

If coronavirus (COVID-19) is detected in wastewater, the next steps depend on whether the detection is consistent with clinical testing results in that area.

As positive cases of coronavirus (COVID-19) have been detected across Victoria, the locations where viral fragments are detected in wastewater are frequently consistent with clinical testing results. No extra public health actions are needed in those areas.

In areas where there are no known  active or recent positive cases of coronavirus (COVID-19), a positive wastewater testing result may provide an early warning and indicate there may be people within that community who have not been diagnosed, but have or have recently had coronavirus (COVID-19). This may also have been due to a visitor to the community.

Depending on the location and context, this can prompt increased or targeted wastewater testing, and public health advice for individual testing and other hygiene and preventive measures in local areas.

A repeated positive result in a local area suggests that it is more likely due to a local community member who may have coronavirus (COVID-19) rather than visitors to the community.

Does a positive wastewater test result mean that there is an active case of coronavirus (COVID-19) in a local area?

No. While a positive wastewater test result may be due to a person with coronavirus (COVID-19) being in the early active infectious phase; it could also be because someone is continuing to “shed” the virus after the early infectious period. It can take several weeks for someone to stop shedding the virus. It may also due to a visitor having been in the community.

Is wastewater testing new?

Poliovirus, norovirus and adenovirus are routinely monitored in wastewater around the world.

Other Australian states and territories are also participating in the national ColloSSoS project. The European Union has a similar active wastewater surveillance collaboration. Canada, the Netherlands, New Zealand and Turkey have also incorporated wastewater testing as part of their coronavirus surveillance.

Will wastewater testing replace other testing for coronavirus (COVID-19)?

No. Wastewater testing is being developed as an additional and complementary tool to the existing public health response and testing of people.

If there are viral fragments in wastewater, does this mean that recycled water or treated wastewater poses a public health risk?

No. Wastewater samples used for testing are taken at the influent (or entry pipe) to wastewater treatment plants.  

Wastewater is treated to kill a wide variety of microorganisms, including viruses, before it is returned to the environment.

There is no evidence that coronavirus (COVID-19) can be spread via recycled water nor via treated wastewater released to waterways.

The following factsheet has further information relating to hygiene, water and sanitation for coronavirus (COVID-19): https://www2.health.vic.gov.au/about/publications/factsheets/hygiene-water-sanitation-covid19

Is my drinking water safe?

There is no impact on your local water supply from wastewater testing. Drinking water supplied by water utilities is safe to drink and for normal household uses.