Wastewater samples from 11 residence halls on the Pullman campus are being regularly collected and screened as part of the university’s efforts to contain the spread of COVID-19.
The targeted screenings are designed to quickly identify and contain potential infections before they can become outbreaks by requiring COVID-19 testing among those who live in and visit a specific campus facility. Public health officials note that those who are infected with the virus that causes COVID-19 can become infectious to others several days before they start to feel ill.
The process has already been put to the test. Following a positive test result of a sample taken from Global Scholars Hall in January, 81 students were notified that they needed to get tested for COVID-19. University staff used building access data to determine who entered the building during the relevant time period.
“We saw good compliance among the students who were asked to seek out additional COVID-19 testing,” said Guy Palmer, professor of pathology and infectious diseases and one of the leaders of WSU’s COVID-19 task force. He noted that all of those tests came back negative.
A second residence hall with a positive result was detected last week, with one of the 88 students testing positive and being placed into quarantine.
WSU Pullman launched its ongoing targeted screening program on Jan. 4. The process involves collecting wastewater samples from each building twice a week. The collection process is straightforward, with a staff member using a long pole with a receptacle on the end to scoop up the sample.
From there, the sample is taken to the Allen School for Global Animal Health, which runs it through a centrifuge to separate out the sediment. It’s in that sentiment where researchers find the RNA that they need to determine whether the virus is present in the wastewater from a given facility. The sample is then transferred to the Washington Animal Disease Diagnostic Laboratory where the RNA is converted into DNA and then made to replicate itself through a process known as polymerase chain reaction, or PCR.
A sample is considered positive if it is detected within 40 PCR reproduction cycles. In the case of the Global Scholars Hall screening, the virus that causes COVID-19 was detected on the 37th cycle.
“The results indicate it could be that an infected individual used the facilities, it could be someone was previously positive, as the virus will shed in stool long after stopped transmitting, or it could be false positive in the lab, which is rare but does happen,” Palmer explained. “We treated this situation as if it indicated one or more positive individuals were in the building, and tested everyone that had access to that facility on that day, which all have been negative.”
That broad response is necessary because, unlike with nasal swabs, the sample collected cannot be tied to a specific person. It’s why samples need to be collected from the outflow of a specific building, and why samples collected from a site like the Whitman County Wastewater Treatment wouldn’t be as helpful because any positive samples couldn’t be tied to a specific building.
The university anticipates as many as 3,000 students may be required to seek out additional COVID-19 tests as a result of targeted screening processes.
In addition to screenings on the Pullman campus, the WSU lab is also running samples collected twice a week at each of Pullman’s elementary schools. All of these tests have been negative so far, Palmer said. Results typically are available 24 hours after samples are submitted.
While no other off-campus testing is taking place, it’s possible that it could be done at apartment complexes in the College Hill neighborhood. The difficulty would come in determining who was at a building at a specific time if a sample comes back positive. It’s also possible that WSU could analyze samples from Pullman’s middle and high schools once students return to in-person learning, Palmer said.