by Maria Letourneau
This week’s post at Pretty Light Science features an article by a guest author, who happens to be a great scientist and a friend of ours. Maria Letourneau is currently a post doctoral fellow at the US Environmental Protection Agency (EPA) in Washington DC working on water quality standards. She completed her PhD in Marine Science at the University of Georgia in May 2020 studying dissolved organic matter composition and dynamics. She earned her BS in Marine Science, Biology and Classics with a minor in Chemistry from the University of Miami in 2015. She lives with her husband, dog and two cats and enjoys reading scary stories, watching bad tv, exploring new places, and drinking local beer. Maria has a passion for the environment and helping others engage with science. A pretty much perfect mix as far as we at Pretty Light Science are concerned.
As we all know, COVID-19 is still an ongoing concern and has caused major upheaval for countries all over the world. With no end in sight, lots of people are worried about how we can overcome the virus. One of the major steps we need to take is better testing. We need to better understand who has the virus and who is not infected. In an ideal scenario, every person would be tested so that researchers would have precise information about where the virus has spread. Unfortunately, that is not a feasible solution and perfect information rarely, if ever, exists. As an alternative means to measuring the number of cases, researchers are using wastewater testing to track the spread of COVID-19. This post will go over how testing wastewater can tell us how far COVID-19 has spread through certain communities WITHOUT having to test each individual person.
Why do we need wastewater testing?
Knowledge is power and the more we know about a problem, the better we can tackle it correctly and defeat it. If we know where COVID-19 is most prevalent in a community, city, state, or country, resources can be better allocated to areas that are in greater need. What makes this difficult for COVID-19 is that some people are asymptomatic, meaning they have the virus but do not feel sick. People who are positive for COVID-19 but are asymptomatic still spread the virus to others but can do so without realizing it because they are not showing symptoms associated with the virus. Screening these asymptomatic people quickly and effectively would be one of the best ways to decrease the risk of transmitting the virus to others but people who are asymptomatic are less likely to ever be screened because why get tested if you don’t feel sick, right?
If we know where COVID-19 is most prevalent, we can more effectively allocate resources to areas that are in greater need.
So how else could researchers get an idea of how far COVID-19 is spreading through different areas? One way that researchers have screened others in the past for other diseases such as poliovirus, hepatitis A and norovirus, is through the monitoring of wastewater. The same methods of data analysis are possible now regarding COVID-19. Data collected from wastewater can provide an estimate of the number of infected people in a given population. This method for COVID-19 testing is being used around the world, and can be especially valuable for countries with fewer resources, or with larger populations, where widespread testing may not be an effective option. This information is especially valuable now because these estimates include both symptomatic and asymptomatic people. All people have to do to provide data is go to the bathroom!
https://www.azbio.org/tempe-halden-covid-19-wastewater
How does testing wastewater work?
Hopefully by now you agree that wastewater testing can be a key tool to monitor COVID-19. The next step is understanding how the process works. What happens is that viral particles are shed through feces and end up in wastewater. When researchers test the wastewater they find the viral particles and viral RNA (this is like DNA but a little different, check out the website HERE to learn more about the differences between DNA and RNA viruses). The viral RNA is usually present in small amounts, so scientists use a technique called polymerase chain reaction or PCR to copy and amplify the RNA enough to be able to identify it. When the RNA is identified, the researchers can then estimate how many people may be infected in the tested community. The science still can’t determine the exact number of people infected, but it can provide an idea of how widespread the infection rate may be.
Ahmed, W. et al. (2020)
https://www.bosterbio.com/protocol-and-troubleshooting/molecular-biology-principle-pcr
Will it replace in person tests?
While this technique may be a good way to estimate how severe the spread of COVID-19 may be in a certain area, it’s not accurate enough to tell us precisely how many people are infected or where they live. Wastewater testing is a good way to compare the spread of the virus between locations and help decisionmakers determine where to use funds to limit spreading. Wastewater testing is a good early warning system to see where hotspots may happen and help mitigate spreading. The best way to use wastewater testing would be in a two-step process alongside clinical testing. Where wastewater testing would identify hotspots in specific communities that have higher infection rates and then clinical testing would be used to identify the infected individuals in those hotspots.
Wastewater testing provides infection estimates for both symptomatic and asymptomatic people.
What’s next for wastewater testing?
By now I’m hoping that you can see how powerful wastewater testing can be! It’s a cost and time effective way of testing a whole community (rather than one person at a time) for COVID-19. It allows us to know how many people are infected even if they are asymptomatic. This helps us mitigate a weakness of clinical testing. Most people who don’t have symptoms won’t go get a COVID-19 test. But with wastewater testing we can estimate how severe the infection rate is of a particular community without having to use individual tests.
So what’s the next step for this research? The most important aspect of this analysis that could be improved is the estimation of the number of people infected output from the RNA data. Improving this estimate would be done by better calibrating the signal marker for COVID-19, that is, having a better idea of how many viral particles are shed for each infected individual. This would make this method a more quantitative way to measure outbreaks, rather than a more comparative approach to assessing outbreaks between different communities. Additionally, scientists say there needs to be more research on all aspects of this type of analysis, including sampling methods, preserving the virus RNA for longer amounts of time before it breaks down, and better data interpretation. But for now, wastewater testing to analyze the spread of COVID-19 and to identify hotspots where local governments can focus their assistance is a great way to use time and money effectively to limit the spread of COVID-19.
Wastewater testing is a good early warning system to see where hotspots may happen it is a great way to effectively use resources to limit the spread of COVID-19..
Cheney Orr/Bloomberg/Getty Images
References:
https://www.azbio.org/tempe-halden-covid-19-wastewater
https://www.bosterbio.com/protocol-and-troubleshooting/molecular-biology-principle-pcr
Hart, O.E., & Halden, R.U. (2020). Computational analysis of SARS-CoV-2/COVID-19 surveillance by wastewater-based epidemiology locally and globally: Feasibility, economy, opportunities and challenges, Science of The Total Environment, https://doi.org/10.1016/j.scitotenv.2020.138875.
Kumar, M., Patel, A.K., Shah, A.V., Raval, J., Rajpara, N., Joshi, M., Joshi, C.G. (2020). First proof of the capability of wastewater surveillance for COVID-19 in India through detection of genetic material of SARS-CoV-2, Science of The Total Environment, https://doi.org/10.1016/j.scitotenv.2020.141326.
Mao, K., Zhang, H. & Yang, Z. (2020). Can a Paper-Based Device Trace COVID-19 Sources with Wastewater-Based Epidemiology? Environmental Science & Technology, 54 (7), 3733-3735 DOI: 10.1021/acs.est.0c01174
Ahmed, W., Angel, N., Edson, J., et al. (2020). First confirmed detection of SARS-CoV-2 in untreated wastewater in Australia: A proof of concept for the wastewater surveillance of COVID-19 in the community, Science of the Total Environment, https://doi.org/10.1016/j.scitotenv.2020.138764
Hellmér, M., Paxéus, N., Magnius, L., Enache, L., Arnholm, B., Johansson, A., Bergström, T., Norder, H. (2014). Detection of pathogenic viruses in sewage provided early warnings of hepatitis A virus and norovirus outbreaks, Applied Environmental Microbiology, 80, pp. 6771-6781
Asghar, H., Diop, O.M., Weldegebriel, G., Malik, F., Shetty, S., El Bassioni, L., Akande, A.O., Al Maamoun, E., Zaidi, S., Adeniji, A.J., Burns, C.C., Deshpande, J., Oberste, M.S., Lowther, S.A.(2014). Environmental surveillance for polioviruses in the global polio eradication initiative, Journal of Infectious Disease, 210, pp. S294-S303
Daughton, C. G. (2020). Wastewater surveillance for population-wide Covid-19: The present and future, Science of the Total Environment, https://doi.org/10.1016/j.scitotenv.2020.139631
Comments