The UC San Diego campus / Image via Shutterstock

Turds tell tales, and UC San Diego is listening.

As the beginning of the school year nears, the university is preparing to ramp up its testing of sewage for the coronavirus. The goal: Monitor the progress of the pandemic on campus and catch outbreaks before it’s too late to control them. Along those lines, UCSD on Saturday sent out its first campus-wide email alert about the detection of the virus in sewage from one of its seven colleges.

Poop — and urine and other bodily fluids — are at the center of the effort since the human body secretes the coronavirus that causes COVID-19. Sewage analysis tests are sophisticated enough to detect one infected person out of 100,000 who are flushing toilets and taking showers, said virologist Charles Gerba of the University of Arizona, who’s been working on a project to test Tucson-area sewage for the virus.

“You can survey an entire community, can get an idea of the number of infected people, and see whether trends are going up or down,” Gerba said. And, he said, the tests can act as an early warning system by alerting officials that people in a community like a dorm are infected a week before they might become sick enough to seek tests on their own.

UCSD has been testing sewage for more than a month from two clinics, a research building and a dorm, said microbiologist Rob Knight, director of the Center for Microbiome Innovation. (Several thousand students have lived in UCSD dorms over the summer, including many from other countries who remain on campus over the break.)

Knight said a researcher tests UCSD wastewater samples each day. “So far, we have seen the coronavirus only in the samples from buildings in which we know COVID-19 patients are housed,” Knight said prior to Saturday’s email alert, which let students and staff know that the virus had been found in wastewater from the Revelle College campus. The virus apparently came from someone who used a restroom there from 6 a.m. and 9:30 a.m. on Sept. 2. The email said: “Thousands of people are on the UC San Diego campus every day, including members of the public. This test is an early indication that one of them is shedding the virus, viral shedding starts before symptoms develop.”

Cases of virus detection may rise as a smaller-than-normal contingent of about 11,000 UCSD students returns to live on campus this month before the fall quarter begins on Sept. 28. The university is embracing a mix of many online courses and a smaller number – about 12 percent of the total – of in-person classes.

UCSD and the University of Arizona have plenty of company on the poop patrol front. According to the Washington Post, researchers are testing sewage at colleges across the country for signs of the coronavirus. (This isn’t a new idea: Scientists have tested sewage for signs of illness such as polio for decades.)  Locally, San Diego State University – home to an intense outbreak – is not testing its sewage, a spokesman said. The University of Arizona, meanwhile, has tested sewage from the municipal San Diego wastewater system.

The key to testing is the viral RNA of the novel coronavirus – its genetic code. The human body sheds bits of the virus in poop and pee (“so much for the myth that urine is sterile,” the University of Arizona’s Gerba said) plus blood and potentially other bodily fluids too.

Poop from infected people includes about 1 million bits of virus per gram, he said.

Sewage tests seek out those virus particles by searching for specific genes. If they find virus particles, researchers amplify them to figure out how many there are – a rough guide to how many people are infected among those who contributed feces and bodily fluids to the sewage sample.

“We’re taking a sample and using it to extrapolate to something larger,” said microbiologist Marc Johnson of the University of Missouri. He’s helping to spearhead a project to test public wastewater in the St. Louis area.

“For wastewater testing, it doesn’t matter how much clinical testing is offered, it doesn’t matter how old the patients are, it doesn’t matter if they are symptomatic or not, it doesn’t matter if they have health insurance, it doesn’t even matter if they believe in the virus,” he said. “As long as they aren’t pooping in a bucket, we can detect their infection.”

Sewage testing has already revealed two small COVID-19 outbreaks at the University of Arizona. First, in August, testing revealed signs of the virus in sewage from a dorm with 310 residents, Gerba said. “We estimated by the concentration that two to five people were infected. The next morning, they tested all the students, found three who were infected and removed them from the dorm. Then the sewage went negative.”

None of the infected students had symptoms.

Later, testing revealed signs of the virus in two dorms where 29 students ultimately tested positive and were removed, Gerba said. “It seems to be working fairly well. We’re hoping that it prevents major outbreaks.”

The sewage tests each cost $250 to a few hundred dollars and take about eight hours, researchers said. In Missouri, the sewage samples are small, only about a quarter-cup, and they don’t stink because researchers “filter out all the solids,” said Johnson, delicately.

At UCSD, researchers are planning to dramatically expand the sewage testing program as students return to campus, said microbiologist Knight. The university is now offering free COVID-19 testing to employees and to students who come to campus, and it hopes to launch a regular testing program for asymptomatic students and staff by October.

As of Sept. 1, the campus reported 43 positive COVID-19 cases among students out of 4,588 tests and 24 positive cases among campus employees out of 3,462 tests.

Randy Dotinga

Randy Dotinga is a freelance contributor to Voice of San Diego. Please contact him directly at

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