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After hurricanes, why is it so hard to test for waterborne diseases?

Six weeks ago, Hurricane Florence dumped 9 trillion gallons of water across North Carolina. Where exactly does all of it go?

As hurricanes move inland, their rainfall swells rivers. Waters rush downstream, collecting waterborne contaminants from flooded out sewage pipes and animal waste from industrial farms. Massive storms like Florence also knock out the power for water pumps, so food, clothes and people go unwashed for days.

On Wednesday’s PBS NewsHour, special correspondent Cat Wise reveals a new effort to expand water quality testing during disasters through the use of drones. The project relies on a tag team. An aerial fleet would spot typically “invisible” spills from above, while a team of boats cruise through the tainted water to directly measure its hazardous ingredients.

Based on interviews with medical professionals and independent state surveys provided to the PBS NewsHour, we now know that Hurricane Florence correlated with localized upticks in two known waterborne pathogens: salmonella and campylobacter.

Here’s how these “disease drones” could waylay these kinds of bacteria outbreaks in the future.

Why waterborne diseases may go unnoticed during floods

After flood waters strike, state and federal officials can usually only conduct a limited amount of testing for water quality. One reason is the scale of these disasters. Monitoring all of the contamination sources — which would require multiple samples over time — is a gargantuan task.

During Florence, for instance, scientists at the North Carolina Department of Environmental Quality were forced to evacuate along with everyone else in the area. They couldn’t return until the floods receded, so days passed between when coal ash pits and industrial farms overflowed into waterways and when their fieldwork began. And even after they arrive on the scene, officials typically concentrate their efforts on sites where spills have already been reported — so some contamination may go undetected.

“Flood waters, in general, pose a real problem because you have so much area to cover, and so many things that it’s possible for you to test for,” said Rachel Noble, an environmental scientist at the University of North Carolina-Chapel Hill Institute of Marine Sciences in Morehead City. “You could test for heavy metals, or maybe for contaminants stemming from hospital waste. There are literally hundreds or thousands of things that we could test the flood waters for.”

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Her team has developed a rapid, hypersentive test for E. coli that can detect a single copy of the bacteria’s DNA as it floats through the muck of a flooded environment. Their procedure can turn around an accurate result within 40 to 45 minutes. That outpaces standard water quality assessments, which can take two or more days to complete, or put a different way, more than 48 hours in which people could be exposed to potentially deadly pathogens.

On its own, Noble’s test is speedy, but her lab is still forced to collect water samples by hand and transport them to the lab. That’s why she teamed with a pair of marine biologists — Dave Johnston and Rett Newton of the Duke Marine Lab — who specialize in studying animals with drones. Together, trio has designed drones capable of locating sewage or storm water spills — even if they involve underwater pipes. (If you’re wondering how it works, you should really watch Cat’s segment).

Why it matters

Rachel Noble hopes these expedited surveys will one day be useful for people like Dr. Vicky Morris, an infectious disease specialist in Morehead City. “The main thing that I think we’ve noticed is an increase in the number of salmonella cases,” Dr. Morris said. “Recently we’ve had two or three cases of salmonella a day, when typically, we might have one or two a week.”

Morris said the uptick in salmonella cases could have been due to contaminated food, agricultural runoff or inadequate hygiene due outages in running water.

Curious about this development, the NewsHour asked the North Carolina Department of Health and Human Services how many people suffered from six common waterborne bacteria before and after Hurricane Florence: campylobacter, cryptosporidium, salmonella, shigella, vibrio, shiga-toxin-producing E. coli.

The data, which focused on six coastal counties heavily impacted by river flooding and storm surge — Brunswick, Carteret, Craven, Duplin, Jones, New Hanover and Pender — showed that the weekly rate of campylobacter infections had increased in two counties — Brunswick and Duplin — after the storm by 46 and 157 percent, respectively.

These upticks involve handfuls of patients, so don’t go away thinking that coastal Carolina is suffering from an epidemic of campylobacter. The data simply illustrates a point made by Morris.

As Morris told Cat during our trip in October, some patients may catch rare diseases during hurricanes like Florence that are difficult to decipher on symptoms alone.

“This patient had a skin, soft tissue infection and also blood cultures that were positive for an unusual organism called Shewanella putrefaciens. As the name implies, it’s a pretty nasty bug,” Morris said. She isn’t kidding. Shewanella putrefaciens tears away at skin and soft tissue, leaving behind blisters that can grow into open wounds. When there is no flesh around to munch on, the bacteria can also consume uranium.

Shewanella putrefaciens infections in humans are typically rare, but the germ is common in various types of water — freshwater, brackish, salt water. Hurricanes cause substantial intermingling between these waterways, which can expose people to this disease and others.

Better testing after events like Florence “would also help us target our efforts towards which particular pathogen, or organism is causing the most problems,” Morris said. “The response to that organism might be different depending on what it was.”