An "unprecedented" spike in COVID-19 viral load in wastewater collected from San Diego County's primary wastewater treatment facility has been noted by UC San Diego School of Medicine researchers.
The amount of COVID-19 virus detected in wastewater has predicted the region's COVID-19 caseload up to three weeks ahead of clinical diagnostic reports, the researchers said Saturday. Since people with COVID-19 shed the virus in their stool even before they experience symptoms, wastewater screening acts as an early warning system.
"The wastewater screening results reported on Friday are unlike any the team has seen before," said Jackie Carr of UC San Diego Health.
Both delta and omicron variants of the virus were detected in the wastewater.
"This confirms prior county reports that omicron is already here and circulating in our community," said Dr. Wilma Wooten, San Diego County's public health officer.
"This is the steepest curve in viral load we've seen since we began screening wastewater in the summer of 2020, and it's continuing to get worse faster than ever before," said Rob Knight, professor and wastewater screening leader at UC San Diego School of Medicine.
Researchers and public health officials said they hoped the warning would encourage the local community to step up efforts to help mitigate the expected surge. In addition to wearing face masks in indoor public spaces, as recently mandated by California, they urged people to get their vaccines or boosters if they haven't already done so.
They also recommended downloading the CA Notify exposure notification system to smartphones, limiting time spent indoors or unmasked with others, and taking steps to improve indoor ventilation and air filtration.
"In addition, every person in San Diego County needs to have a low threshold for testing right now," said Christopher Longhurst, chief medical officer and chief digital officer at UC San Diego Health. "Don't wait. If you feel the slightest symptoms, if you think you might have had contact with someone with COVID-19, if you've gathered in crowds without masks, if you're planning a get together — test, test, test."
COVID-19 PCR tests are available at UC San Diego Health, various San Diego County sites, other health providers and community pharmacies. At-home rapid antigen tests are available from retail pharmacies and online vendors. Anyone who tests positive for COVID-19 should consult their health care provider.
San Diego County has only one primary wastewater treatment facility, in the Point Loma neighborhood. All excrement flushed away by nearly two-thirds of the county's residents, including those on the UC San Diego campus, ends up there.
UCSD researchers pick up wastewater samples that had been collected and stored for them by lab technicians at the treatment plant. They bring the samples to a lab at the La Jolla campus to test them for the COVID-19 virus, along with wastewater samples collected from more than 350 campus buildings. All positive samples are sequenced to track viral variants.
The team can detect even a single infected, asymptomatic person living or working in a large building of more than 500 people on the UCSD campus. They have found that notifying the occupants of each building with positive wastewater increases COVID-19 testing rates by as much as 13-fold. The approach has enabled early detection of 85 percent of COVID-19 cases on UCSD's campus, officials said.
And this information is important to people like Dr. Jess Mandel, chief of pulmonary and critical care medicine at UC San Diego Health. He said this data confirms what they’ve been expecting.
"We’re really preparing ourselves for the next wave of COVID infections that we’ve been expecting for some time," he said. "And with the emergence of the omicron variant, in where the timetable I think has shifted up but this is a very infectious variant and we expect to see a spike very soon."
This forecasted surge couldn’t be hitting at a worse time, Mandel said.
"I think the troubling thing for us is that this occurs on a backdrop of the hospital being extremely busy with non-COVID patients as well," he said. "And so you know the system is already being strained a little bit by everything else that’s going on and now we’ll probably have a big upsurge in COVID on top of it."
Hospitals are already seeing a steady rise in cases but most of the serious infections continue to be among the unvaccinated, Mandel said.
Despite local hospitals having plenty of personal protective equipment and other supplies on hand, Mandel and other doctors are worried about omicron being a game-changer.
"Really what we’re most concerned about is having enough people," he said. "Really the human resources because this variant is so infectious we expect that doctors, nurses and other folks will get infected along with others in the community and that really impacts our readiness and our ability to field the team."
So they are urging their staff to be extra vigilant
"We’re all in this together. That's what gotten us through and that’s what carries the day," Madel said. "But really, again, asking all of our folks to be incredibly careful, to, you know, mask like lives depend on it because they really do."
