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COVID-19 in San Diego wastewater starting to increase

Erik Jepsen / UCSD
A UC San Diego scientist collects wastewater from a collection unit on campus in this undated photo.

Early COVID-19 indicators hint that the virus’ transmission is growing in San Diego.

Viral load in local wastewater typically goes up before the number of cases start to rise. Recent data from water treatment plants shows the amount of COVID is beginning to rise again.

"I don't think people should be overly alarmed about this early uptick," said UC San Diego Health's chief medical officer Christopher Longhurst. "We’re keeping an eye on it and as a health system we’re taking precautions."


Longhurst said up until about a week ago the viral load from Point Loma Wastewater Treatment Plant samples was steadily falling, even dipping under 1,000,000 copies per liter. The peak during the omicron surge was 47,000,000 copies per liter, officials are seeing a slight increase to 2,000,000 copies per liter.

"It's enough that we're sitting up and taking notice," Longhurst said.

In response to the increases UC San Diego Health is testing more patients and resuming masking in areas where it was previously optional.

"The community standards right now are very reasonable for a relatively low prevalence of disease," Longhurst said. "So if you’ve got underlying disease or are otherwise high risk, take note, be cautious. I think for the rest of us lets keep an eye on what’s going on."

About 80% of the recent COVID-19 found in wastewater is being identified as the BA2 sub-variant of Omicron. That strain is more contagious and likely what is driving surges in Europe.


"We’re not really sure what’s going to happen," Longhurst said. "It’s unusual and unexpected that we’re seeing another surge so quickly after the last one. On the other hand we know that the antibodies that this virus creates probably washout after just three or four months which means that the people who got infected back in December are susceptible yet again."

Longhurst said the good news is that the BA2 variant appears to have a less severe impact than previous strains. He said COVID-19 booster doses are especially important for those who are at high risk. San Diego County has one of the state’s lowest booster rates, with 42% of the eligible population opting for them so far.