Scientists around the world are studying the novel coronavirus (SARS-CoV-2) from many different perspectives in an effort to better understand how it infects humans and spreads from person to person. The goal is to identify this spread, find therapies for neutralising and eliminate it. One approach being taken by researchers is to examine wastewater to track coronavirus infection trends. Researchers at the University of Sheffield are developing new techniques that could be used for a number of potential uses including to identify a second wave of the pandemic. Vanessa Speight, Professor of Integrated Water Systems, Department of Civil and Structural Engineering, University of Sheffield, UK, in a conversation with Raelene Kambli explains more about this research
Can you elaborate more on the current research work undertaken by your team and the key findings?
The University of Sheffield was part of an international expert group who worked to develop consensus on methods and approaches to monitor wastewater systems for the presence of SARS CoV-2 virus genetic material. The key findings are:
- monitoring wastewater for SARS CoV-2 genetic material could be useful in identifying occurrence and trends in COVID-19 infection at a community scale.
- guidance on sampling protocols.
- a prioritised list of further research needs to better develop this approach to understand infection in communities.
How can wastewater be a source to detect the occurrence of SARS-CoV-2?
Several studies have demonstrated that people infected with COVID-19 shed viruses in their fecal matter. So, we can take samples from the sewer network to look for the virus to get an overview of its occurrence across the area that the sewer network serves. Some early monitoring work in the Netherlands showed that the virus was present in wastewater and mirrored trends in increasing cases (https://www.medrxiv.org/content/10.1101/2020.03.29.20045880v1).
We do not yet fully understand how much virus is released for different individuals during different stages of disease. So, that is a further area of active research that will help refine this approach. It is important to note that the tests detect the genetic material of the virus, not the actual virus itself. Hence, there is no way for these tests to indicate whether the virus is alive or dead, only that it was once present.
Can wastewater reveal changes in the infection pressure as well?
Tracking the presence of the genetic material over time can show if there is a rising or falling trend in coronavirus presence in the community that is being sampled. So, this detection could be helpful in showing when infection rates are increasing, possibly even to identify particular areas within a community that have higher rates of infection or to identify that a second wave of infection appears to be starting. Right now, we do not have enough information to translate the genetic marker data into an exact number of infections, but this is an active area of research. We believe that this information is most valuable as additional information alongside traditional public health information on testing, cases, etc. rather than serving as a standalone measure of infection.
So, you say that this research is significant to track a second wave of COVID-19?
Yes, if the wastewater samples show a large increase in virus genetic material above historic levels, it could be an indication that a second wave is taking place. Note that this research was focussed on communities with centralised sewerage systems. There may also be the potential to sample in decentralised wastewater facilities like latrines but that has not been attempted yet to my knowledge.
Do you know of any scientific evidence that states its effectiveness, apart from that of the University of Sheffield?
The Dutch study mentioned above was one of the first to demonstrate the link. Since that time, several others have emerged and many countries are working to quickly develop the laboratory capabilities and many have already begun the sampling. A recent study from Australia has just been published (https://www.sciencedirect.com/science/article/pii/S0048969720322816).
In the past, has wastewater been utilised to analyse other pathogens?
This approach has been used successfully in the past to monitor illicit drug use and other pathogens like polio.
What inferences can we gather from past experiences/studies to understand the second wave of COVID-19?
We are learning from the current testing to understand what background levels of virus genetic material can be expected, so that we can identify if an increasing trend really does show a second wave of infection arriving. This information should be used alongside other public health information rather than as the only measurement of infection.
So, for this purpose, a country will need to set up sewage surveillance on a national level, right?
This sampling is typically done at a wastewater treatment plant. So, this surveillance is at a community level.
How does a country go about doing that?
At this point, it is important to develop laboratories with the appropriate capabilities to process and analyse samples. The Water Research Foundation expert group developed guidance about sampling protocols but this is a rapidly evolving field of knowledge. The output from this work is freely available at the website: https://www.waterrf.org/event/virtual-international-water-research-summit-covid-19. Central coordination of laboratory techniques and procedures will make it possible to compare results from different labs to get a better national picture of COVID-19 occurrence.
Countries such as Denmark and the UK are following sewage surveillance to analyse wastewater and understand pathogen. What can India learn from them?
Coordination on analytical methods and close cooperation with the public health authorities to share data will be critical to the success of this type of monitoring.