A Novel Approach to Tracking COVID-19

Tracking COVID-19 in sewage could be an effective way to monitor the spread of the virus in densely populated urban areas. Photo: Thijs Degenkamp
Tracking COVID-19 in sewage could be an effective way to monitor the spread of the virus in densely populated urban areas. Photo: Thijs Degenkamp

By Christian Walder, Neeta Pokhrel

Testing sewage for the coronavirus could provide vital clues to its spread in areas where mass testing is difficult.

Developing countries are grappling with how best to fight COVID-19. Locking the countries down further will cost trillions of additional dollars. For Asia and the Pacific, the estimated economic impact of COVID-19 is estimated at $2.5 trillion (9.3% of regional GDP) under a 6-month containment scenario, with the region accounting for 30% of the overall decline in global output.

Some countries are starting to open up but the implications and the risks between lockdown and reopening are far from clear. Getting the right balance is particularly challenging when countries know their limited resources to test, track, and isolate cases cannot possibly cover the millions of their citizens. Is there a way to supplement their existing capacity?

Water, sanitation, and public health professionals see potential for using sewage to track the prevalence of COVID-19 in communities.

For centuries, the outbreak of diseases and threats to public health have primarily been linked with water and sanitation. Most famously, Dr. John Snow in 1854 traced the source of the cholera outbreak in London to a single water well and solved it by removing the handpump. More recently, since 1988, surveillance of sewage has been successfully used to monitor polio outbreaks around the world.

Health departments of most countries routinely use information from sewage to gain insights on public and environmental health. For instance, recent advancements in sewage monitoring have allowed authorities to draw conclusions on drug consumption in cities and potential impacts on aquatic ecosystems.

Water, sanitation, and public health professionals see potential for using sewage to track the prevalence of COVID-19 in communities.

The potential of monitoring sewage to track the prevalence and dynamics of COVID-19 infections in population was discussed among professionals, researchers, water utilities, and government departments as early as January 2020. In the past few months, research groups have successfully traced the virus in sewage influent as well as in the sludge from sewage treatment plants in the Netherlands, the United States, Sweden and other countries.

COVID-19 symptoms may take up five days to present whereas individuals can shed the virus already, in their feces, prior to developing symptoms. In the Netherlands, a clear correlation between the community infection rate (increase in the reported COVID-19 cases) and the increase of the COVID-19 concentration in sewage was observed. Traces of COVID-19 was found in sewage as early as six days before the first symptomatic case was detected.

Water professionals from various sectors – researchers, academia, government, utilities and bilateral and multilateral development partners – are currently discussing the wider applicability of this approach for both developed and developing countries and how best to scale up from the proof of concept and piloting stages. This includes the development of detailed sampling and testing protocols for sewered, non-sewered and on-site sanitation systems.

A number of initiatives such as the global sewage surveillance project and platforms, led by the World Health Organization (WHO) and partners, are bringing together professionals from across the world to discuss, identify best practice examples, promote knowledge sharing and collaboration.

The Asian Development Bank is working with WHO and other partners to bring best practices to countries in Asia and the Pacific. This includes harnessing and sharing the latest findings and developments on the wider applicability of tracing COVID-19 in sewage and boosting investments in hand-hygiene in developing countries—the most cost-effective defense against COVID-19.

Countries will and should continue to closely monitor the COVID-19 pandemic by testing symptomatic cases. However, attention is warranted to track and isolate, testing and tracing it in sewage as an early warning and a relatively affordable tool for decision makers.

This will be all the more important for countries that do not have capacities to test the masses at large scale.

Testing every individual in the megacities of the developing world for COVID-19, and increasing testing capacities to deal with volumes needed as others in the developed world have, may not be possible in the timeframe that we need.

Sewage surveillance could thus be a powerful and a much more affordable tool, not only for COVID-19 infections but also other public health indicators, to alert and inform the decision makers in developing countries.

Together with other tools and data, this would help them to decide where to take extra precautionary measures, where they need to tighten or to ease restrictions.