Measures to prevent SARS-CoV-2 transmission through wastewater in poor regions
By Dr. Liji Thomas, MDNov 15 2020
Scientists worldwide strive to understand how coronavirus disease 2019 (COVID-19) and the novel pathogen that causes it – severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2) – spreads.
A new paper published in the journal Science of the Total Environment on November 10, 2020, discusses the reality of the virus’s wastewater transmission. Overall, the researchers found that wastewater transmission would have a disproportionate impact on countries with low development indices.
Study: Snowballing transmission of COVID-19 (SARS-CoV-2) through wastewater: Any sustainable preventive measures to curtail the scourge in low-income countries? Image Credit: Gameanna / Shutterstock
Routes of SARS-CoV-2 transmission
The COVID-19 pandemic has brought about immense uncertainty about how and when the SARS-CoV-2 virus spreads and the best strategies to contain it. At present, respiratory droplets or aerosols, including airway mucus or sputum and saliva, as well as direct contact infected individuals, are known to be routes of transmission.
Other routes are suspected, however. For instance, recently, fecal shedding of the virus has been demonstrated from patients with a spectrum of COVID-19 severity. Urine has also been shown to contain the virus RNA. However, sewage from both hospitals and the community at large has been shown to contain viral RNA. Scientists now wonder if and for how long the infectious virus can persist in wastewater, treated and untreated.
No study has confirmed viral transmission through water contaminated with the virus, but some researchers report that the virus quickly becomes non-infectious in wastewater. However, if the possibility of wastewater-driven viral spread does exist, it raises an alarming scenario concerning low-income countries.
Contamination of groundwater by wastewater
In many such regions, the sanitary system consists of pit latrines, often situated near the source of groundwater, such as a well. Many segments of the population do not use even a pit latrine. In the absence of training or facilities, many use any open spaces for defecating, and this may occur close to surface water sources.
In other settings, wastewater is collected but is then released untreated into the environment and may thus contaminate the groundwater source. In all such situations, such sources provide drinking water, and if contaminated with the infectious virus, may lead to large-scale infections in the community.
Decentralization of wastewater treatment
- Majority of population likely has pre-existing immunity to SARS-CoV-2, claim researchers
- SARS-CoV-2 antibodies wane, depending on age, symptoms and ethnicity
- SARS-CoV-2 viral antigens found in non-pulmonary tissues in recovering patients
The current study examines various measures to prevent such spread. One method is decentralized wastewater treatment facilities for all healthcare centers concerned with COVID-19 patients. This would cut off isolation and quarantine centers and other COVID-19 treatment centers, from discharging infected sewage into the same cesspool as the surrounding community. This in turn, will make it unlikely that the community source of groundwater is contaminated by the virus, whether open well or stream.
Testing wastewater for the virus
Large-scale COVID-19 testing is not feasible in many low-income countries with a large population. This has led to widespread infection due to the mixing of infected individuals with others. Several researchers have pointed out the potential for wastewater testing to identify potential hotspots before switching to individual testing in such regions. This may be more effective than symptom-based screening, say many researchers, besides being more economical.
Thus, the authors of the current paper say, “The resourcing of field and laboratory facilities for community-wide monitoring and testing should be one of the major priorities of the governments of low-income countries.”
A third recommendation is a very old one: improve sanitation and provide safe water for household purposes. In 2016 alone, there were around 830,000 deaths linked to unsafe water and poor sanitation or hygiene worldwide. Untreated wastewater causing groundwater contamination has given rise to outbreaks of respiratory infection, gastroenteritis, filarial and other parasitic infestations. Thus, providing good sanitation should be a primary goal in handling COVID-19.
The development of point-of-use water decontamination devices is a priority area that can help treat water and make it safe for use. Some low-cost technologies now available include iron-oxide bio-sand filters, zero-valent iron filters, nanocellulose – and gravity-based ultrafiltration. Some suggest that to boost the efficacy of these devices, ultraviolet irradiation, ozonation, and chlorine could be added.
Finally, education of people in low-income settings, especially in rural areas, about the potential severity of COVID-19, as well as about the importance of sanitation facilities to avoid wastewater discharge into open water sources, is crucial.
Overall, therefore, policy interventions to inform people of the threat as well as to promote safer behavior around sources of groundwater are a major requirement in this situation, in addition to technological and testing solutions. Considering the scope of the threat, these recommendations deserve serious attention to prevent increasingly severe transmission rates in poverty-stricken areas of the world.