Masks are back on at UCSD Health as coronavirus level rises in San Diego wastewater

Smruthi Karthikeyan (left) and Rob Knight collect wastewater samples on the UC San Diego campus.
(Erik Jepsen / UC San Diego)

Less than a week after operating in the least-restrictive “low prevalence” level of its COVID-19 plan, UC San Diego Health told employees March 24 that some restrictions will return immediately due to an increase in the amount of coronavirus recently detected in local wastewater.

SEARCH, a coalition of local institutions that has been testing local effluent for more than a year, posted an update late March 23 that 2.1 million viral gene copies per liter were detected at the Point Loma treatment facility two days before, nearly double the 1.2 million per liter found one week earlier.

Dr. Christopher Longhurst, the UCSD Health system’s medical director, said experts gathered March 24 and deemed the increase statistically significant enough to take action, especially since the upper boundary for operations at the lowest level of precaution is 1 million per liter.

“The wastewater now suggests we’re seeing a significant uptick in transmission, and as a health system, we’re taking this step as a precaution,” Longhurst said.

At the height of the January coronavirus surge, the reading reached over 47 million per liter.

The biggest change is that thousands of non-clinical health system workers who were able to take off their masks as the new operating plan took effect March 21 now will have to put them back on. There is no change in doctor’s offices, hospitals or other clinical settings because state law has continued to mandate face coverings in those locations.

At the health system’s “medium prevalence” level, workers will again be encouraged to work remotely, whereas a hybrid approach — a blend of in-person meetings and working from home — was the new order of the day under the lowest level of precautions.

Patients will notice little difference, though those who are not fully vaccinated against COVID will again have to be tested before undergoing a medical procedure. That requirement was removed in the low prevalence category.

UCSD is the first large public organization in the region, and likely one of the first in California, to peg its pandemic response to the levels of virus tracked in wastewater, reasoning that the indicator can provide an early warning when a surge is building. Testing, by comparison, can take longer to show a spike, especially with many people using home tests that do not communicate results to health departments.

Thus far, most organizations have not made a similarly direct connection between operations and changes in wastewater virus levels, but the information is getting increased attention from public health departments. Dr. Seema Shah, medical director of San Diego County’s epidemiology and immunization department, said the public should view such increases alongside other more familiar signs and signals, such as the number of new cases appearing daily and the number of people being hospitalized with COVID.

With 321 new cases reported in the county March 24, and most recent numbers over 300, she said it has continued to be clear that there is more virus circulating in the community than anyone would like, yet it also is obvious that most have discarded their masks as spring approached. Increasing wastewater numbers, she said, simply reinforce what was obvious: The virus is still spreading and a new surge is likely.

“It’s a warning sign,” Shah said. “The wastewater numbers are nowhere near as high as they were back in January, but when you see an uptick like that, the first thing you should think is, ‘I need to be more cautious.’”

— La Jolla Light staff contributed to this report.