Testing COVID-19 in wastewater.
COVID-19 testing numbers are dropping in the US. And that’s bad news.
Without testing, there is no way to keep track of where the pandemic is headed and whether the vaccines are working. “While the public may view vaccination as a priority right now, and it is a priority, widespread testing still is essential for infection control” — said Romney Humpries, medical director of the Clinical Microbiology Laboratory at Vanderbilt University Medical Center.
“I think wastewater has proven itself as one of the most, I would say, objective means of understanding what SARS-CoV-2 is doing in our society,” — said Gertjan Medema, a microbiologist at KWR Water Research Institute in the Netherlands.
The US has recorded an average of about 1.5 million COVID-19 tests per day over recent days. And this is about 26% fewer than the average in mid-January. If we do not test, we will not know how much infection there is.
Besides diagnostics, testing is being used to determine quarantine requirements and tracking the evolution of the pandemic. People need to realize that they need to go and get tested when they are experiencing symptoms.
In California, we saw a decreased testing volume in the last 5 weeks. The seven-day average went down to about 181,000 tests per day from about 230,000 tests per day.
With high vaccination numbers, people believe they don’t need to be tested anymore. And they could not be more wrong.
How can we solve this?
Viral genome sequencing of wastewater can detect symptomatic, asymptomatic, and pre-symptomatic people. It can also detect new SARS-CoV-2 variants before they are detected by local clinical sequencing, according to a new study published in mBio, an open-access journal of the American Society for Microbiology.
The opportunity to track SARS-CoV-2 mutations in wastewater could be very interesting. It will allow local communities to help determine whether the vaccines are working or not and inform public health decision-making as an early warning system. Scientists do not yet know whether the new emerging variants, like the Indian, Brazilian, and South African variants,are more infectious or resistant to the vaccines. Hence, it is crucial to keep testing and tracking the spread of COVID-19. Another reason to continue testing is the fact that variants are hard to prevent from spreading. For example, we see that the British variant has spread to more than 50 countries. This is where testing of wastewater for COVID-19 can play an important role.
So let’s say the end is not near yet. It is clear testing will stay relevant and it will be important to detect COVID-19 rapidly. Governments will be looking for solutions that can detect COVID-19 faster, and prevent further outbreaks. Testing wastewater seems to be a compelling additional solution, on top of the current COVID-19 testing.
There are some more advantages to testing wastewater as infectious disease surveillance:
- Sewage testing has been successfully used in the past as a method for early detection of other diseases such as polio.
- SARS-CoV-2 can be shed in feces of individuals with symptomatic or asymptomatic infection; therefore, wastewater surveillance can capture data on both types of infection.
- Nearly 80% of the United States households are served by municipal sewage collection systems.
- Quantitative SARS-CoV-2 measurements in untreated sewage can provide information on changes in total COVID-19 infection in the community contributing to that wastewater treatment plan.
- Depending on the frequency of testing, sewage surveillance can be a leading indicator of changes in COVID-19 burden in a community.
- SARS-CoV-2 RNA detection in sewage works as a COVID-19 indicator that is independent of healthcare-seeking behaviors and access to clinical testing.
- SARS-CoV-2 RNA detection in sewage can be cheaper, compared to testing members of the community individually with a classic COVID-19 test.
The Centers for Disease Control and Prevention (CDC) and the US Department of Health and Human Services (HHS), are initiating a system in response to the COVID-19 pandemic, the National Wastewater Surveillance System (NWSS). The data generated by NWSS will help public health officials to better understand the extent of COVID-19 infections in communities.
The National Wastewater Surveillance System is currently ramping-up efforts through partnerships with state, local, tribal, and territorial health departments. The system provides funding, technical support, a national data repository and other resources that will allow state and local health departments to navigate the long-term monitoring.
Wastewater surveillance is not a replacement for clinical testing, but it can be an efficient, and cost-effective addition to the current testing. Not everyone has the same access to healthcare and COVID-19 clinical tests. Those people and communities aren’t really getting the full big picture, whereas for wastewater testing, you are able to test the whole community at once.
Although there is still a lot to learn, even the small pilot projects that started last year, have already helped identify hidden viral hot spots and figured out how to target these.
These systems could ultimately help officials stay ahead of emerging threats, providing early warnings about whatever pathogen is poised to cause the next pandemic.
