‘Guerilla Epidemiology’: How Palm Coast Sewers Are Helping Guide Health Department’s Covid Strategy

The Centers for Disease Control just two weeks ago announced a nationwide wastewater surveillance initiatives based on sewage testing, which it says “over time can provide trend data that can complement other surveillance data that informs public health decision making.”

Now it’s been deployed in Palm Coast.

The idea isn’t to detect the incidence of covid in specific individuals or even specific streets (households on septic systems are not included), but to measure it by neighborhood. It can help predict a coming outbreak: infected individuals typically don’t know that they’ve been infected until they develop symptoms or are tested after having been exposed to those who’ve been confirmed positive. The predictive approach can serve as a viral weathervane, an early-warning system of where the next outbreak is incubating. It can help the health department steer testing sites to a particular neighborhood. It can ensure that more testing is done where it’s needed most in hopes containing community spread.

That’s already happening. The Flagler Health Department is using the first results of the city’s “sewage epidemiology” to open a testing site at the Italian American Club in the F Section today, and to open another testing site at Mt. Calvary Baptist Church on Pine Lakes Parkway next week.

“People may not realize that when somebody has this infection, they may be shedding millions of viruses per very small amount of fluid in their mouths or other body sites,” Dr. Stephen Bickel, the medical director at the Flagler and Volusia health departments who originated the idea for Palm Coast, said Wednesday during the city’s weekly town hall on the virus. The sensitivity of testing effluents can be “profound,” Bickel said, as has been shown in European cases. Months ago he proposed the idea to Palm Coast government, which owns its own utility.

It’s been implemented since, with the city sectioned off into six geographical regions.

“They do a variety of adjustments for the volume of wastewater, the number of people in the area,” Bickel said, explaining how what he’s termed “guerilla epidemiology” works in this case. “Then you can compare each area to itself or to time periods to see trends. It’s very useful in terms of data gathering. We use it for three things. One is, if we’re not getting any cases in an area, which hasn’t happened lately, but did happen in May and June and April, we can see if there’s any activity that we’re missing, because it might pick it up in the wastewater before we pick it up in any individual. So it alerts us to focus our testing efforts on certain areas.

“Secondly, for each of these six regions, we can compare each time period to the time period before it and see how that region is doing. If it’s doing worse, again increase our testing. If it’s doing better, it gives us some reassurance. The third thing is, we can use this for the whole area as one other trend measurement to correlate with our case numbers, our positivity rate, our ER visits, our hospitalization rate, to get at a kind of a complete picture of how we’re doing with Covid in our community. So it has a lot of potential uses. We’re still learning about those. Those are the ones I envisioned initially when I proposed this.”

Palm Coast then added a new dimension, overlaying its incidence maps with maps of confirmed cases, with particular attention to the locations of schools and assisted living facilities or nursing homes. “If we show an area where the wastewater is high, the cases are low, maybe we want to do more testing there. If we show an area where it’s the opposite, maybe the trends are changing,” Bickel said. “What we’re really trying to do here is be very strategic in our attack on the spread of this.”

Though long in planning and discussed on occasion at council meetings and by Bickel and Bob Snyder, the health department chief, in interviews over the past months, the working system and maps were unveiled for the first time at Wednesday’s weekly covid-19 town hall anchored by Mayor Milissa Holland. “This truly is pretty innovative,” she said. “It’s exciting to see how we can then take that data and evaluate a strategy moving forward, in particular with the reopening of schools.” (Superintendent Cathy Mittlestadt was among the officials speaking by phone at the town hall, though she did not address the sewer testing.)

“This initiative was all about public health, public safety and the welfare of our community,” City Manager Matt Morton said. “This was so we could make data-driven decisions. It wasn’t data for data’s sake. It’s data that will directly and has directly served our community. It’s those analytics that come from the data that have helped us, and will help us to continue to support the quality of life we all want and to support our local economy.”

Snyder showed a map identified as one of the six sections, covering the F-Section and parts of the C-Section. “The wastewater analysis did show a quantifiable detection of the virus” there, Snyder said. “This is one of two sections where that is the case. We also noticed that there are positive cases in this area as well. We decided to strategically get a community testing site in this area, so right to the north of Section F, the Italian-American Club, has been identified and graciously has provided their club and their parking lot for drive-through covid-19 testing to occur.”

Another section indicated no current, quantifiable presence of covid-19, though the area was a relative hot spot in the last two weeks, with confirmed positive cases in the double digits there, adding to a lot of cases cumulatively. The area covers parts of the R and B Sections, and led to the decision of opening the testing site at Mt. Calvary Baptist Church starting next week.

Bickel said there would be weekly reports of the sewer testing data.

“The final pathways is finding the individuals that are spreading it to other individuals, that’s why the testing is so emphasized,” Bickel said. “But this allows us to target the testing. The more available, the more people are going to do it. It also raises awareness in communities. It’s part of a comprehensive strategy that includes testing. But this really helps us direct our efforts.”