SAN DIEGO _ Scientists have found an unexpected ally in the fight against COVID-19 _ a tool so powerful, it might help zero in on coronavirus outbreaks before they happen.
It's your poop.
The science of sewer surveillance, also called wastewater epidemiology, is being harnessed by the largest university in San Diego County to help stay on top of COVID-19 cases among students.
And while San Diego is not actively using feces to try and predict COVID-19 hot spots, the city is participating in several studies to better understand this potential monitoring technique.
So how exactly is excrement being used to combat this disease?
When people are sickened by the novel coronavirus, remnants of the virus are expelled in human waste. Scientists have discovered that those viral remnants stick around _ even after excrement is flushed down the toilet and whisked off to a wastewater treatment plant.
This suggests that by testing sewage in municipal treatment plants, researchers could determine whether the coronavirus has infiltrated a particular community _ before cases start to show up.
In one recent study, Yale researchers sampled sewage in New Haven, Conn., for more than a month. About a week after concentrations of viral remnants started to climb in sewage samples, COVID-19 testing totals also started to climb. The climb in coronavirus concentrations found in the wastewater was a warning that an outbreak was on its way.
The metrics public health officials currently use to track COVID-19, like test totals, are lagging indicators. It may take days for a sick person to develop symptoms and days more for someone to get a test. During that time, an infected person may already be spreading the coronavirus throughout their community. Not to mention the people who are carrying the virus, but aren't experiencing symptoms at all.
Sludge is different.
"As viral shedding can occur before cases are detected, we hypothesize that the time course of SARS-CoV-2 RNA concentrations in primary sewage sludge is a leading indicator of outbreak dynamics within a community served by the treatment plant," the report reads.
Although the study has not been peer reviewed, other researchers found the results promising.
"That gives you precious more days to do something," said Ian Pepper, an environmental microbiologist at the University of Arizona who is also studying the presence of the coronavirus in sewage.
Pepper and his team have been analyzing wastewater samples from cities across the country, including San Diego. Their goal is to calculate how much novel coronavirus genetic material is in each sample and then compare it to local case totals.
He hopes the study will reinforce that "sewage surveillance gives us an extra window of opportunity to work against the pandemic."
Some _ like health officials at the University of California, San Diego _ have found the existing science so compelling that they're already planning on weaving it into their COVID-19 testing and surveillance strategies.
Dr. Robert "Chip" Schooley, an infectious disease specialist at UC San Diego Health, said, by fall, the university expects to begin testing the wastewater from all of its dorms on a weekly basis.
In an effort to refine its strategy, the university first plans to test wastewater from Jacobs Medical Center, where a known number of COVID-19 patients are being cared for. That will begin in the next week or two.
Earlier this month, the college unveiled its Return to Learn program, which, among other things, aims to broadly test students, faculty and staff members on a recurring basis. Schooley said wastewater testing could help shape that testing effort.
For example, if students on campus are consistently testing negative for the virus, the school could choose to pause recurring testing and focus, instead, on sewage samples. If traces of the coronavirus start to show up in excrement, that could be a trigger for officials to start doling out testing again.
"You're using it as a way to help direct your individual testing in a more intelligent way," Schooley said.
So far, 1,400 students still living on campus have been tested. None has been positive.
Sewage monitoring has been used to study and monitor viruses before _ most notably in the effort to eradicate the poliovirus. Although a polio vaccine was developed in 1952 by Jonas Salk, transmission still exists in several countries.
Like those infected with the novel coronavirus, an individual with polio may not experience symptoms. To zero in on potential outbreaks, scientists have looked for remnants of the virus in community wastewater.
Although communities across the state are beginning to ease social distancing restrictions, a COVID-19 vaccine isn't expected any time soon. That means public health officials have to be constantly vigilant, ready to quickly identify and isolate those who are sickened or exposed to the novel coronavirus.
That's challenging because many infected people experience mild symptoms or no symptoms at all. But whether you're showing signs of sickness or not, the proof is in the poop.
