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Scaling back on wastewater testing leaves the most vulnerable behind
Wastewater surveillance, in contrast, provides the ability to know what is happening in all segments of the population, and often with enough resolution to provide tailored advice to vulnerable communities or high-risk settings. (Pexels photo)
During the COVID-19 pandemic, wastewater surveillance had critical scientific and policy importance while also providing clear and easily interpretable data to the public about the threat we faced.
The decision to greatly curtail the program in Ontario, arguably the flagship model in the country, raises important questions about the future of public health surveillance.
Why was wastewater so important for infectious disease surveillance? Advances in pathogen detection make it a rare trifecta in public health terms: comprehensive, timely, and low cost.
First, disease that is severe enough to come to medical attention through patients is almost always the tip of the iceberg – surveillance based on tests on individuals, while very useful, is narrow and highly biased. Wastewater surveillance, in contrast, provides the ability to know what is happening in all segments of the population, and often with enough resolution to provide tailored advice to vulnerable communities or high-risk settings.
Second, it provides information early enough in a wave of emerging disease to allow an appropriate response from government officials and the public. For example, wastewater detected mpox when one person in a population of more than a million was infected. This provided weeks of lead time before the general population risk became significant, meaning that individuals could take precautionary steps such as updating their vaccines, and health systems could prepare for an expected rise in severe illness.
Third, this technology is incredibly cost-efficient. Although estimates are slightly fuzzy – an issue of transparency on top of public health concerns – a recent estimate placed the operating budget at an upper bound of $15 million for the province of Ontario – $1 per person per year – which is affordable compared to most forms of surveillance.
Wastewater analysis uses remarkably flexible technology in its potential applications, not just for COVID, but for numerous other viruses, including RSV, mpox, and both avian and human influenza. It is also useful for tracking and responding to the opioid crisis and for population exposure to toxins and hormones, and promising for monitoring the increasingly dangerous pandemic of antimicrobial resistance.
We don’t know what a future “Disease X” will be, but wastewater surveillance will almost certainly be a vital part of an adaptive early warning system to protect Canadians.
Dramatically scaling back a key tool
In 2023, more than 100 wastewater testing sites operated across Ontario, providing coverage for 75 per cent of the population. The Public Health Agency of Canada took over this program as of last week, with only four established sites around the city of Toronto (covering 20 per cent of the population of the province), with four more sites planned to be operational before this winter.
This striking loss in surveillance capacity has important equity implications, hampering the ability to detect disease spread for rural Canadians, those in smaller communities, and those in northern parts of the province – many areas where access to acute care is already reduced.
And the COVID-19 wave that is currently emerging highlights additional equity issues that arise as surveillance capacity winds down. With no public health measures in place, decision-making around COVID protection has been mostly downloaded to the individual, with strategies like masks or vaccination being the only option.
Data is key to good decision-making for individuals, not just governments
But how are individuals to make decisions without the information required to assess risk? How this summer wave develops (an issue that the mixed trends in final posted wastewater results last week make a cliffhanger) is a perfect example of the challenges that emerge.
For instance, updated vaccines will be available only in the late fall as companies ramp up production of a version that targets the KP.2 variant. But many high-risk individuals had their last dose of vaccine more than six months ago and will be waiting another three months with waning protection while viral spread potentially increases around them.
Should these individuals go out and get vaccinated now with last year’s version of the vaccine or wait for the updated version that more closely matches what is currently circulating? That is a good reason for shared individual decision making between patients and their providers, guided critically by data on risk – except that the very surveillance information that would guide this risk assessment has just become unavailable for many.
Looking out on the sweltering August landscape, COVID is rightfully and thankfully well out of mind for most Canadians. But greatly curtailing a program which has shown fundamental value for Canadians, enhanced equity, and our ability to care for those who are most vulnerable, fails to meet the minimum expectation of public health practice.
The absence of this information makes healthcare decisions more difficult for the most vulnerable among us and for those who live in already under-serviced parts of our country. It also leaves all of us less prepared to respond to future epidemics and pandemics.
This article first appeared on Policy Options and is republished here under a Creative Commons license.
