MIAMI — In March, when it became clear that the U.S. was facing an unprecedented pandemic, Miami-Dade County began sampling its sewage as a potential tool for measuring the extent of COVID-19 infections. The hope was that testing the county’s poop for the coronavirus could serve as an early warning indicator of a dreaded second wave expected in the fall.
Now, with cases rising all over the country and Florida experiencing a steady increase to levels not seen since August, what is the sewage saying?
The short answer: Not much, at least not yet. The process got off to a slow, messy start but they’ve cleaned up the data and there is still some promise it will work.
For months, the county has been paying $3,600 a week to see if testing sewage could help estimate coronavirus infection trends in the population. Miami-Dade’s Water and Sewer Department sends samples from its three wastewater plants to a specialty lab in Boston called Biobot.
The results were meant to help former Mayor Carlos Gimenez and public health experts get ahead of the virus and potentially save lives by better preparing hospital infrastructure for surges. After all, everybody poops, and wastewater reflects all individuals in a community, whether they have COVID-19 symptoms and access to testing or not.
Because the coronavirus shows up in human waste just a day or two after infection, mining wastewater for COVID-19 data emerged as another COVID-19 gauge. Used in conjunction with other data, it could help provide a sense of where the COVID curve might be headed.
But while cities like Paris and Boston have integrated wastewater testing results in their strategies to fight COVID-19, WASD says the turnaround time on test results is not yet fast enough to make it a planning tool in Miami-Dade.
“We need to have more confidence in the data. The results at this point are mimicking testing data that’s coming to us from the state,” said WASD director Kevin Lynskey.
Miami-Dade Water and Sewer takes weekly samples from its wastewater treatment plant in Virginia Key as part of a COVID-19 testing program.
Lynskey said that the Biobot data are still mostly a look back at the COVID curve, rather than forward for indication of trend. For example, recent Biobot analysis of Dade’s sewage shows case number estimates started to trend up around mid-October, but there is no data available yet after Oct. 27 because of sampling delays by the county, Lynskey said.
Problems have come at both ends of the process — the collections of samples from the county’s three major sewage plants and the analysis of it by Biobot.
When sampling started in March, the results were unreliable, with spikes and drops that made no sense when analyzed against the clinical and testing data of COVID-19 patients tracked by the Florida Department of Health, Lynskey said. Biobot admits that its methods needed improvement after it launched the testing program in March.
Until August, Biobot’s algorithm was estimating the prevalence of the virus, or how widespread the disease was in the population. Because the lab was still fine-tuning its technology, results were taking as many as two weeks to get back, and the testing…