Researchers are getting some progress in the wastewater angle of SARS-CoV-2. And according to an expert, four questions have been answered, including the transmission risk.
The four questions about SARS-CoV-2 in wastewater were answered by an associate professor at the University of Notre Dame. The answers pointed out how the coronavirus is monitored in wastewater and what is the likelihood of transmission. While studies have not found live and infectious SARS-CoV-2 in treated wastewater, there is a concern in those who are working in treatment facilities. They answered the questions in The Conversation, a not-for-profit media network for researchers.
How Germs are Monitored in Wastewater?
Wastewater is a perfect environment for germs to grow and spread in cities. This is the reason why scientists have been monitoring pathogens in wastewater since the 1940s. One of the pathogens that can spread through this is the poliovirus. A person with polio can contaminate the environment or wastewater through their feces. As such, polio outbreak management is often augmented with wastewater monitoring. Nearby rivers and streams are tested as well to track down the outbreak's origin.
Unfortunately, there is no true standard in monitoring germ wastewater. Scientists can obtain samples and test them in labs. While water treatment facilities can apply molecular tools to detect the presence of viral RNA. Though, RNA is extremely tiny and can be tricky to detect in limited samples. They have to be clever to get the best samples and use methods to obtain the most accurate results.
For COVID-19, research in SARS in 2003 showed the coronavirus' presence in human fecal matter. And since SARS-CoV is related to SARS-CoV-2, there is a chance that COVID-19 patients can excrete viral particles.
What Does it Mean if SARS-CoV-2 is in Wastewater?
At the University of Arizona (UA), a US public research university, researchers conducted surveillance testing of SARS-CoV-2 in its wastewater. The testing was induced by the spike of COVID-19 cases at its dorms. The overview found that individuals who unknowingly spread the disease were asymptomatic. They were living in one of the university's dorms. The coronavirus was detected in wastewater samples from campus housing sites.
"We did test — I think there are 311 individuals in that dorm — and we did the antigen test yesterday and found two positive cases there," said UA President Robert Robbins.
UA had been testing the dorms and other campus buildings for COVID-19. The early discovery of SARS-CoV-2 in campus wastewater likely prevented a true outbreak. If UA failed, the campus would have faced a major health crisis from within due to asymptomatic individuals. Those who tested positive were quarantined, and after they tested negative, they were allowed to return to the dorm.
Kyle Bibby, an associate professor of environmental engineering at the University of Notre Dame, said that wastewater testing is key in learning COVID-19 trends. If the test shows a high concentration of SARS-CoV-2, then COVID-19 infections are likely increasing within a community. The results can explain the puzzle in the number of cases. If the viral load is high and the cases are low, it may indicate many asymptomatic patients.
However, the viral load in human fecal matter varies per person. One person can excrete about 100 copies of the SARS-CoV-2 genome per gram of feces. While another can excrete 100 million copies per gram. That is a huge difference and must be considered in studying COVID-19 trends in cities. Regardless of variables, wastewater data can guide the government and healthcare sector to better decisions.
Can Wastewater Increase the Transmission Risk?
It is unclear if the novel coronavirus can be spread via water. In a study published in The Lancet Gastroenterology and Hepatology journal, researchers investigated the fecal-oral transmission route of COVID-19. They noted that from 2002 to 2003, SARS caused several cases of diarrheal symptoms in patients. About 16% to 73% of SARS patients developed diarrhea in the first week of infection. The RNA of SARS-CoV was detected in stool samples from the fifth day of illness. The levels of viral RNA in the stool specimens peaked on the 11th day of infection. After 30 days of SARS infection, a small number of patients still had viral RNA in their stool samples.
In 2012, the emergence of MERS rattled the world of a new illness. Among patients, 25% infected with MERS-CoV developed diarrhea or stomach pain. One research team found 14.6% of stool samples from patients positive of MERS-CoV RNA. Their investigation of the samples revealed that MERS-CoV respiratory infection was secondary to intestinal infection.
In the early reports of COVID-19 in Wuhan, China, 2% to 10% of patients experienced gastrointestinal symptoms, including diarrhea, vomiting, and stomach pain. Stomach pain was more common among patients admitted to intensive care units. The stool sample from a patient in the US was detected with SARS-CoV-2 viral RNA. The result even revealed the binding mechanism of the novel coronavirus, which is more sophisticated than SARS-CoV.
Bibby believes that SARS-CoV-2 may be spread via water, though, it is not yet demonstrated. Respiratory droplets remain the most dominant transmission route of COVID-19. Studies in wastewater mostly found inactivated coronavirus in fecal matter. It is not a significant concern for the public but a big worry for workers in treatment facilities. Because they can be exposed to untreated wastewater, workers must wear personal protective equipment to avoid COVID-19 and other infectious diseases.
What are the Other Challenges?
The main challenge is the limitation in the detection. Even if several random samplings are conducted, lab results may yield negative readings. It does not mean that COVID-19 is no longer in a city. It only suggests that not every patient excretes viral RNA. This shows the difference between testing wastewater and testing bodily fluids.
Another challenge is the lack of framework in the wastewater screenings for COVID-19. Data from lab tests must be interpreted and translated properly. Otherwise, the local government unit may get the wrong message. No every drop in cases means that everything is normalizing. Something may simply be changing and influencing the number of cases.
Fortunately, advancements produced new tools that can be used to detect environmental factors linked to COVID-19. These tools may aid the patterns of case clusters and narrow down areas where asymptomatic carriers are most likely located.