Scientists are well aware that coronaviruses such as SARS-CoV-2 which is responsible for COVID-19, can remain active for several days in wastewater and drinking water, posing a potential public health risk. They are now calling for more research to help them determine the best method of keeping the novel coronavirus out of the water cycle, and propose that developed countries should provide financial assistance to help developing countries improve and/or expand water treatment infrastructure to prevent further COVID-19 outbreaks in the future.

According to an editorial piece that was recently published in the Royal Society of Chemistry's journal Environmental Science: Water Research & Technology, the coronavirus can be carried in airborne aerosols, essentially tiny water droplets, which enter the atmosphere via spray or evaporation. The authors suggest that further testing needs to be conducted to ascertain whether current water treatment methods are effective at killing coronaviruses, including the novel coronavirus responsible for COVID-19.

"The ongoing COVID-19 pandemic highlights the urgent need for a careful evaluation of the fate and control of this contagious virus in the environment," said Haizhou Liu, an associate professor of chemical and environmental engineering at the University of California, and co-author of the paper. "Environmental engineers like us are well positioned to apply our expertise to address these needs with international collaborations to protect public health."

While there have been no known COVID-19 cases arising from sewage leaks, SARS-CoV-2 (the virus responsible for COVID-19) is closely related to the virus responsible for SARS, which has seen outbreaks stemming from this source, as occurred in Hong Kong in 2003, where a local cluster of SARS cases was attributed to aerosolization.

The authors also point out that the SARS-CoV-2 virus could potentially colonize biofilms lining water pipes supplying homes with water from public water systems, which would make shower-heads a potential source of aerosolized COVID-19 transmission, in the same manner that Legionella bacteria responsible for Legionnaire's disease is transmitted.

Fortunately, modern water treatment methods are thought to be effective at killing or eradicating coronaviruses in both wastewater and drinking water. However, the authors caution that the effectiveness of many of these treatment methods have not been tested, specifically when it comes to coronaviruses such as SARS-CoV-2, and they recommend that further research in this regard would be beneficial.

The authors also suggest that wastewater and drinking water treatment facilities in outbreak hotspots —which may receive SARS-CoV-2 contaminated water from places considered high-risk for COVID-19 outbreaks, such as nursing homes, community clinics and hospitals — should be upgraded. For example, ultraviolet light systems could be installed to disinfect water as it enters into the public water treatment facility.

According to the authors, drinking water systems that recycle wastewater back into drinking water also need to be thoroughly investigated to ensure that coronaviruses are removed, and may also require the introduction of new disinfection regulatory standards to ensure water is virus-free and safe for consumption.

The authors are also concerned about the potential for the virus to colonize biofilms— the thin layer of bacterial slime that lines water pipes in older drinking water networks — and suggest that it may be necessary to monitor coronaviruses in biofilms in order to prevent COVID-19 outbreaks.

Following the global COVID-19 pandemic, there has been a surge in the household use of antibacterial and antiviral agents and disinfectants, which could potentially lead to antibiotic resistance in bacteria found in the environment. The authors suggest that treated wastewater discharged into freshwater systems should be closely monitored throughout the entire water cycle, and are calling on chemists, microbiologists, environmental engineers and public health specialists "to develop multidisciplinary and practical solutions for safe drinking water and healthy aquatic environments."

In conclusion, the authors point out that developing nations and even some areas within developed nations such as rural areas and poorer communities, which lack basic water treatment services to remove common water contaminants are likely not able to remove coronaviruses such as SARS-CoV-2 either. These areas may be prone to frequent outbreaks of COVID-19 that are then spread as infected people trade and travel globally. Because we live in an increasingly globalized world, it is in the best interests of developed countries to support an fund the provision of improved water and sanitation to regions that desperately need this, if they hope to limit future outbreaks and halt the global spread of diseases and pandemics such as COVID-19.

"It is now clear to all that globalization also introduces new health risks. Where water and sanitation systems are not adequate, the risk of finding novel viruses is very high," said Professor Vincenzo Naddeo, director of the Sanitary Environmental Engineering Division at the University of Salerno, and co-author of the study. "In a responsible and ideal scenario, the governments of developed countries must support and finance water and sanitation systems in developing countries, in order to also protect the citizens of their own countries."

Journal Reference Vincenzo Naddeo, Haizhou Liu. Editorial Perspectives: 2019 novel coronavirus (SARS-CoV-2): what is its fate in urban water cycle and how can the water research community respond? Environmental Science: Water Research & Technology, 2020; DOI: 10.1039/d0ew90015j