Public health surveillance is absolutely essential to protect and sustain community health. Health departments monitor community health status and investigate new health hazards all the time. They perform health surveys, and investigate clusters of mysteriously ill citizens. Covid-19 has brought the functions of testing, tracing and surveillance through state and local health departments to an unprecedented scale. With Covid-19, early on we turned away from a narrow clinical health care approach, focusing on those who were sick, to a broader public health, population-based strategy. Public health authorities tested not only those with symptoms, but also a sample of those who were asymptomatic. Surveillance was and is our warning system.
Covid-19 has introduced us to many bold new approaches to surveillance. We can now monitor our water and air and words. Using technologies that were in development before Covid-19, health surveillance will continue to expand in three ways as we see it.
Using wastewater epidemiology–the study of sewage–we are increasingly tracking the spread of diseases. The sewer system is analogous to the human gastrointestinal system. Just as clinicians can make medical judgements about a patient’s health based on a stool sample, we now learn about a community’s disease state by sampling wastewater that comes from sinks and toilets. It turns out that when Covid-19 levels rise in wastewater, daily cases rise soon after. Testing for Covid-19 (or its future viral version) in a city—are rates rising or falling?—can help make decisions about whether schools should stay open, for instance. Over the past few years, the same testing technology has been telling us whether there is an unexpected amount of opioid use in a town, and in the future might monitor stress hormone levels or nutritional deficiencies among citizens.
As with water, we share air. Half of Americans live in counties where air is unhealthy. We share the effects of coal smoke and emissions from agricultural industry, and sometimes, cigarette smoke. Air pollution reminds us that the atmosphere is a communal space. Covid-19 has taught us convincingly that we are at the mercy of what we breathe. We are on the way to marketing devices that can be used to detect a variety of airborne pathogens, including coronaviruses. If proven accurate, these could be deployed in hospitals, offices, schools and other buildings to monitor for signs of Covid-19 as we return to business as usual. As with wastewater tests, but on a smaller scale, air samplers may be able to offer the infectious portrait of a building’s workers over the previous two or 24 hours.
With water and air monitors, we pool large samples as an efficient way to picture a community. Results are anonymous. Similarly, scrutinizing our words on social media is a window into our mental state and health behaviors. The language employed in online posts can be used to screen for conditions like depression or pregnancy. Algorithms searching for changes in the words we use in our private correspondence may serve as signals for monitoring the health of communities in yet another way.
Surveillance provides the data for change at scale. Of course with all surveillance data, figuring out how to respond to a positive language, water or air sample will prove tricky. Thinking through the social costs of these increasing surveillance methods will become an important part of our growing familiarity with these methods. That will be the subject of another The Turning Point.
Michael Stein & Sandro Galea
As we re-emerge from the pandemic, 2021 stands to be a turning point year for public health. In The Turning Point’s weekly essays, we reflect on what we learned during 2020, and what we are learning during 2021, that can guide us to the creation of a better, healthier world.