Wastewater surveillance program

Last Updated: 18 Mar 2022 8:48am

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Tasmania’s Wastewater Surveillance Program tests wastewater (untreated sewage) for fragments of the COVID-19 virus (SARS-CoV-2) at sewage treatment sites across the State. These sites are selected by the Department of Health based on factors including population size, location, and ability to access samples.

The testing process

Testing of wastewater can show if the COVID-19 virus is present in a geographical area and population.

Testing wastewater for the COVID-19 virus can help track infections in the community. These tests provide information to inform the Tasmanian public health response to COVID-19. Untreated sewage will be collected weekly or monthly, and samples transported to the Royal Hobart Hospital laboratory for testing. Results are published on this website weekly.

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Why wastewater is tested for coronavirus

Testing wastewater for the COVID-19 virus (SARS-CoV-2) can help track infections in the community. This information is used alongside clinical testing results to inform the Tasmanian public health response to COVID-19.

Wastewater is all the used water coming from buildings that passes through the sewage system and includes water from toilets, showers and baths, basins and sinks, and laundries. Fragments of SARS-CoV-2 can enter wastewater through an infected person’s faeces and when washed off hands or bodies.

Monitoring diseases through wastewater is common.  Poliovirus, adenovirus and norovirus are routinely monitored in wastewater around the world. Wastewater testing and results do not reflect the quality of your local water supply.

Viral shedding

When someone is sick with a virus, their bodies release virus particles, which are then shed into the environment. This process is called viral shedding.

For people who have, or have recently had, COVID-19, the virus is shed in respiratory secretions (snot, mucus, phlegm) when they talk, cough, sneeze or even when they breathe out. The virus can also be shed in a person’s faeces (poo) too.

It can take many weeks for someone to stop shedding the virus and they can continue to shed the virus even when they are no longer infectious to others.

The COVID-19 vaccine does not contain live virus and does not result in viral shedding in wastewater.

How coronavirus is detected in wastewater

Samples of wastewater are collected on either a weekly or monthly basis from sewage treatment plants at several locations across the state. These samples are analysed for viral fragments. Testing sewage for fragments of SARS-CoV-2 is a specialised test and only a small number of laboratories can perform the test.

Tasmania’s samples are sent to the laboratory at the Royal Hobart Hospital for testing. It can take up to 7 days from when a sample is taken to receive initial laboratory results. The Tasmanian Department of Health is working closely with a number of organisations locally to ensure a high standard of timely testing can be performed.

It is not completely understood how long the viral fragments survives in wastewater but it is known that  it depends on a variety of conditions, including the temperature, other pathogens, and the amount of organic matter. It is important to note that the virus that causes COVID-19 is easily inactivated (‘killed’) by detergents which are also present in sewage (from hand washing at basins, dish washing, etc.).

Detection

There are several situations that could be occurring when COVID-19 viral fragments are detected in wastewater. A detection may be due to:

  • One or more people who are infectious with COVID-19 in the catchment area.
  • One or more people who have recently recovered and are no longer infectious in the catchment area.

People who have recently recovered from COVID-19 can continue to shed the virus for several weeks after they are no longer infectious.  People shedding the virus may have had or may not have had symptoms.  A detection in wastewater could mean a person with COVID-19 may be in the community or has since left the area.

If COVID-19 viral fragments are detected in wastewater, the next steps depend on whether the detection is consistent with recent clinical testing results in that area and the current context in Tasmania. Typically, a public health response team will evaluate the circumstances surrounding each detection and advise impacted communities on further measures if necessary. .

Steps may include:

  • Public health messaging to encourage testing for COVID-19 and reminders about hygiene practices and other precautions; and
  • Increasing testing capacity in the area affected
  • It important that anyone with any symptoms of COVID-19, no matter how mild, gets tested. Read more about COVID-19 testing.

An inconclusive detection occurs when there is a very weak detection of viral fragments that cannot be confirmed by further analysis. This is most likely due to someone continuing to shed the virus who has previously had COVID-19 and is no longer infectious. An inconclusive result is less likely to require a Public Health response, unless there are other reasons to believe COVID-19 might be present in the local community.

There still could be cases in the community if SARS-CoV-2 is not detected in wastewater. Wastewater moves through the sewage network, and so case/s need to be in the catchment area around the time of sampling. It also depends on other factors such as virus shedding by people over the course of their infections, dilution of the virus (which can occur after heavy rains), and presence of microorganisms in the sewage that affect how well the testing can detect the virus. It means viral fragments were not found in testing that particular sample.

Testing in other areas of Australia

Tasmania is joining other Australian states and territories who are participating in the national ColoSSoS project (Collaboration on Sewage Surveillance for SARS-CoV-2) which is coordinated by Water Research Australia. This project brings together health departments, water utilities, laboratories, and researchers from to share knowledge and experiences from this evolving field. Wastewater surveillance for SARS-CoV-2 is being practiced in countries around the world.