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Miami-Dade adopts wastewater epidemiology to help fight coronavirus

MIAMI-DADE COUNTY, Fla. – Innovative early lab tests, research and discussions around the world about using a community’s sewage to help track the contagion during the coronavirus pandemic have progressed into a new surveillance system in Miami-Dade County.

Since the virus’ genetic signature is found in patients’ stool, the wastewater program could help epidemiologists to detect the resurgence of the disease before patients are diagnosed. The data can help public health officials to move to contain specific outbreaks and public officials to evaluate some reopening policies.

Dr. Aileen Marty, an infectious disease specialist with the Florida International University’s Herbert Wertheim College of Medicine, is hoping the program at the water treatment facility can help authorities to get early warnings if there is a second wave and to reduce the cost of testing.

“It has been a way to estimate that the actual number of people who have the virus in their system in a given population is actually much higher than what the test results indicate,” Marty said referring to the asymptomatic patients or the symptomatic patients who avoid testing.

Marty has been advising Miami-Dade Mayor Carlos Gimenez during the pandemic. Miami-Dade has been sending weekly sewage samples from three wastewater treatment plants to Biobot Analytics, a lab in Massachusetts working with plants in about 40 other states in the country.

“We have detected Covid-19 in wastewater and we sent that up to Massachusetts to try and determine the level of infection here in Miami Dade,” Gimenez said. “It’s more prevalent than people think.”

Data shows that so far the highest reading was measured on April 9. It showed that up to 46,000 — 2% of Miami-Dade’s 2.3 million people using the wastewater system — may have been infected. The Florida Department of Health reported there were about 5,745 confirmed cases as of that day.

Potentially worrisome are the recent sewage breaks and overflows in both Miami Dade and Broward County. Though Miami Dade Water Sewer is halfway through completing a $1.8 billion project to upgrade Miami-Dade’s wastewater system by 2026, breaks continue to happen.

Doug Yoder, the deputy director of the Miami-Dade Water & Sewer Department, said this week’s record rainfall has been challenging.

“The last few days of extreme rainfall indicate that systems are designed for a certain capacity but they’re not designed for the largest rainfall that can occur,” Yoder said.

And with hurricane season beginning June 1, Marty warns that “it really behooves us to get a handle on this and make sure that we don’t spill untreated wastewaters into our oceans and into our lakes and rivers.”

Especially now that South Florida is beginning to loosen restrictions. Miami-Dade beaches are set to reopen Monday. The good news is that right now our beaches have never been healthier.

“The data does show that our beach water right now, since there have been so few people in the water, is cleaner than it’s been in a long long time,” Marty says.

In fact, Gimenez believes it’s not sewage spills that contaminate our beaches, but us.

“There’s a lot of skin cells that come off and rub off on the beach,” he says. "That’s actually a contributor that we see and unfortunately when it gets too high we have to close the beaches.”

Marty stresses the importance of practicing good hygiene when going to the beach.

“I think that people should shower when they go in the water and shower when they come out of the water,” she says.

Social distance will be key to preventing the spread of COVID-19 as beaches reopen, but Gimenez says he believes is there is no added risk of catching coronavirus in the ocean.

“We don’t think it travels that well in saltwater, actually,” he says.

In fact, the science is not there yet. There have been no tests to determine if COVID-19 can actually infect us through human contact with contaminated untreated wastewater.

“The actual absolute risk, nobody knows. Nobody knows right now,” Marty says. “And more likely than not it’s very small, but again it’s not zero.”

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