COVID-19 sewage monitoring shows surge in San Diego cases slowing

COVID-19 sewage data now shows San Diego’s record spread of the virus is starting to decline.

“We’re coming out of the surge for sure,” said UC San Diego professor Rob Knight. “However, it is possible that cases will continue to increase or may be peaking now.”

Knight leads the project that has analyzed San Diegans wastewater from the Point Loma Treatment Plan for the past two years. He said sewage is a leading indicator of the spread of the virus, with data typically three weeks before confirmed cases.

“What we’ve seen time and time again is that spikes in sewage are followed by spikes in cases, spikes in hospitalizations,” Knight said. “Although we are out of this highest peak, we are still at very stable levels in the sewage at this point.”

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Using the sewage data, the researchers predicted the record peak in cases ahead of the holidays. Knight said that while we appear to be off the current peak, the amount of COVID-19 found in sewage is about 10 times worse than in mid-December when they warned of record increases.

“The reason sewage is a leading indicator is simply because you get infected in the gut before you get infected in the respiratory tract,” Knight said. “And so, as a result, we see these things in the sewage.”

The drop in numbers is good news for hospitals that are dealing with shrinking capacity, but with thousands of cases still being reported daily, we are not yet out of the influx.

“This is good news for the community, but remember we still have to be careful at this time,” Knight said.

Samples are taken at the Point Loma plant approximately four times a week. They are also from across the UC San Diego campus. The omicron variant constitutes the majority of current waste samples. Knight said because the strain is more contagious, it likely contributed to a larger increase in cases this winter compared to last winter.

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