The testing not only allows for faster results than traditional COVID testing, but UC San Diego researchers say it could be less costly and easier to implement in communities with families who may not want their children tested in schools, out of fear or a lack of trust.
For months, UC San Diego has had a wastewater testing program on its campus that detects shed pieces of the novel coronavirus in feces.
In November, the university started working with San Diego County to extend that program to some K-12 schools and child care centers, said Rebecca Fielding-Miller, assistant public health professor at UCSD who is leading the school testing program.
Here's how it works: a robot that looks like a large canister is installed at each school. It collects samples of wastewater daily to be tested for coronavirus at a UC San Diego lab. Child care staff also send in used diapers for UCSD to test fecal samples of children who are not yet potty-trained.
The results for the samples typically come back in the evening or the following day, within about 36 hours, Fielding-Miller said.
Testing waste for shed pieces of the coronavirus is valuable because coronavirus is believed to show up in feces before a person exhibits symptoms, and potentially before a person would test positive in a PCR COVID test, Fielding-Miller said. A PCR, or polymerase chain reaction test detects the coronavirus' genetic material.
In addition to testing waste, schools and child cares in the UCSD program test the surface of their classroom floors daily for coronavirus. Staff swab a one-square-foot section of the floor in every classroom used that day; the swab will be tested for coronavirus at another UCSD lab.
This surface testing is a new technology, Fielding-Miller said, and this program is helping researchers see how long the coronavirus lives on various kinds of surfaces and which surfaces are best to test for coronavirus.
If any of the wastewater or surface samples test positive for coronavirus, then children and staff at the site will be tested for COVID.
Researchers are using the diagnostic PCR tests to determine specific accuracy levels of the wastewater and surface testing, Fielding-Miller said.
Ten local schools and two child care centers are currently participating in the program, which UCSD calls the "Safer at School Early Alert" system. The test sites were chosen because they serve low-income communities struggling with COVID, including El Cajon, San Ysidro, Chula Vista, Southeast San Diego and Vista.
The program is free to schools because it is funded by the county.
What sets the wastewater and surface approach apart from traditional COVID testing is it allows for anonymous testing of school communities, Fielding-Miller said.
Traditional testing relies on families to agree for their children to be tested for COVID, but there are several reasons why families, especially in disadvantaged or immigrant communities, may be afraid to do that, Fielding-Miller said. For example, families may be wary of how agencies would handle their personal and health data, or they may be afraid to give personal information if somebody in the household is undocumented.
While the wastewater and surface testing does not identify individual COVID cases, it helps schools target when and where schools should deploy COVID testing of individuals, which could help schools save money and testing resources, Fielding-Miller said.
Researchers want to help more schools across the state implement the testing program and are writing a manual so schools and counties elsewhere can implement one.
"What we really wanted to do was create a system where, in the absence of weekly diagnostic testing, we could still have an eye on what's happening in the school and know when it's time to deploy those more expensive resources," Fielding-Miller said.
Here are the local schools participating in the program:
America's Finest Charter School, St. Rose of Lima, Foothill Oak Elementary (Vista Unified), Monte Vista Elementary (Vista Unified), Vista Grande Elementary (Cajon Valley Union), Horton Elementary (San Diego Unified), Castle Park Elementary (Chula Vista), Lilian Rice Elementary (Chula Vista), Smythe Elementary (San Ysidro), Sunset Elementary (San Ysidro). In addition to UCSD's wastewater testing, the county is working to roll out antigen testing to schools, starting with Coronado Unified School District. The district is one of the first two school systems in the state to pilot the antigen testing program, according to the district.
Unlike PCR tests, antigen tests detect proteins from the virus and are typically highly specific but less sensitive than molecular tests.
Coronado students and staff self-swab their nostril, and their sample is inserted into a card-sized testing module. The antigen tests results can come within 15 minutes.
The tests are free and provided by the county. School health staff help conduct and process the tests.
Within the first two weeks of its testing program, Coronado Unified tested more than 1,000 students and staff, said Deputy Superintendent Donnie Salamanca.
"Timely, convenient testing is an essential element to opening schools for in-person learning, and outsourcing is costly and often inconvenient for staff," the district said in a statement.
Routine, asymptomatic testing is not necessary for schools to be open, but experts say it is one of many safety measures to help prevent potential outbreaks within schools, because it can help detect asymptomatic cases before they spread.
Gov. Gavin Newsom has recommended that schools conduct routine COVID testing as frequently as once or twice a week in areas with high COVID spread, and he proposed offering incentive money to schools that reopen to pay for testing. But Newsom's plan was met with criticism from school district leaders, many of whom said the money he proposed isn't enough to conduct testing at the levels he recommended.
The state is offering COVID testing at a discount to schools. Meanwhile, some private schools and school districts, including San Diego Unified and Chula Vista Elementary, have already started their own on-campus pilot testing programs. Although some school districts have not yet reopened for in-person instruction, they are testing students and staff who are participating in limited, on-campus programs the district is holding.
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