Wastewater can sound alarms

When infectious diseases go beyond the expected number of cases, like the present Covid-19, they pose overwhelming challenges to public health monitoring bodies. At such times, an active, early alarm system can reduce the adverse effects.

It turns out that what we flush down our toilets has a wealth of information that could caution us about our wellbeing and health, including the impending danger of outbreaks. Our body regularly eliminates byproducts of food and medicines (metabolites), pollutants, and pathogens through urine and faeces. Stool and urine tests are standard, clinical health check investigation methods at an individual level.

Taking cue from this, wastewater analysis relies on a mass urine and stool examination of people. Raw, untreated sewage effluents are a reservoir of public waste matter which, when screened give valuable insights into the general health of the people in a given region.

Inputs from such an assessment called Wastewater Based Epidemiology (WBE) are providing valuable data to experts. In this new method, real-time, spatially distributed data is collected; quantifiable readings of the elements under scrutiny are measured and extrapolated over the population density. A statistical and epidemiological analysis is applied to the readings from which estimates are drawn. Such mathematical models help in computing the level of distribution of the targeted agent among the people.

WBE was proposed by Daughton et al. in 2001, as a non-intrusive tool at the wastewater treatment plants to monitor the use of illicit drugs in a region. Convinced by the reliable results of this novel approach, several European countries, the USA and Australia began implementing the technique to ensure public health and safety. WBE helped them to determine the public profiles of alcohol, tobacco, pollutants, use of specific medicines, lifestyle diseases and the presence of a few recurring infections.

Now, virologists are applying WBE to scrutinize the new coronavirus. By examining the viral shedding that enters the drains, the patterns of how the virus circulated are emerging. Astonishing results are arising out of these studies.

To cite examples, Italy, the Netherlands, and Brazil performed viral screening in old wastewater samples. In all these regions, the tests revealed that remnants of the viral genetic material existed in the sewage waters well before the first clinically detected case. A few samples from Brazil indicate that the viral signatures were present in their sewages since November – even before China reported its first case.

These outputs are indicative that WBE has the potential to be a powerful tool that can ring the necessary alarm bells. This method may prove to be an early warning system as the conventional clinical identification or self-reporting of cases occur after the disease symptoms have manifested in patients.

The epidemiology reports prompted Italy to launch a pilot study to monitor the wastewaters around its tourist areas. They envisage that WBE will be a strategic tool that can check the resurgence of cases well in advance.

WBE is still in its infancy, and there are several hurdles to be overcome before it becomes a well-established methodology. WBE requires the amalgamation of many disciplines like high-quality sensors, rigorous chemical and biological testing protocols, and real-time continuous monitoring facility at the treatment plants. Designing and developing the sensors is an active and on-going research area, with Australia pioneering in presenting studies on ultra-sensitive, cost-effective prototype sensors.

As of now, there is no record if similar wastewater analysis is done in India. Given that our country is plagued by several recurring infectious disease outbreaks often, applying WBE may yield valuable inputs. By employing rapid monitoring facilities at several wastewater treatment plants can help formulate a hypothesis of disease patterns and exposure risks.

On a larger scale, with global collaboration, WBE can progress into a well-established robust methodology. Correlating the results from different communities may help to investigate the various factors that influence disease propagation. Not just in containing the present pandemic but also influence policymaking in preparedness for future outbreaks.

(The writer is a science communicator)