“COVID is well behind us,” Gov. Gavin Newsom declared at a news conference in late May while discussing his return-to-office mandate for state workers.

But recent data tells a different story. Area doctors and experts say another COVID surge is likely on the way this summer.

For the better part of a year, COVID concentrations in wastewater have stayed at “low” or “medium” levels in Santa Clara County. But since the beginning of May, wastewater COVID levels around the county have increased. While COVID concentrations remain “low” in Sunnyvale and Gilroy, readings have crossed over to “medium” in San Jose and Palo Alto.

Last year, concentrations were at “high” levels from June through the beginning of this school year, only dropping below that threshold in October 2024, and remaining mostly flat and low since then. Other parts of the state show the same pattern.

“It’s been a delightful six months,” said Dr. John Swartzberg, clinical professor emeritus of infectious diseases and vaccinology at UC Berkeley. “We can’t be very sure about what this virus is going to do, but there are very good infectious disease epidemiologists who argue that we will see a summer surge.”

The new variant, NB.1.8.1, appears to be more contagious than other omicron subvariants, and there has been a recent increase in cases internationally, with more expected as this strain spreads and the busy summer travel season kicks off.

“It does appear to have greater transmissibility than its predecessors, and we’ve seen that pattern over and over again,” Swartzberg said. “What this virus is doing is trying to find new hosts.”

During the first several years of the pandemic, cases and deaths spiked most in the winters, though there was often a surge roughly twice a year, in the winter and then again in the summer.

But in 2024, there was a prolonged summer surge in California that lasted from June through the end of September.

After that spike, the expected winter surge never came this year, and for the first time in five years, flu deaths surpassed COVID deaths.

“It’s kind of like watching the clouds get darker,” said Dr. Peter Chin-Hong, a UC San Francisco professor of medicine, who also expects a summer surge. “People are feeling it coming.”

Swartzberg and Chin-Hong say predictions of another surge are based on the increased transmissibility of the new variant, and waning immunity in the population. To complicate matters, in late May, U.S. Health and Human Services Secretary Robert F. Kennedy Jr. said the vaccine would no longer be recommended for most children, or pregnant women, though the CDC official recommendations released Friday countered Kennedy’s statement, and COVID shots for most children is still recommended.

“It’s been great that we’ve gone all these months without a lot of cases, but it means that the baseline immunity in the population is much less,” Swartzberg said.

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Still, “most people have a lot of immunity,” Chin-Hong said, “but some people don’t, or they lose it faster,” like the elderly or those with compromised immune systems. Experts advise those at-risk groups to be vaccinated every six months.

Even for those who are not at high risk, there might be reason to take added precautions as cases rise. Swartzberg, who is planning a vacation, is expecting to take some extra precautions, like wearing a mask and dining outdoors.

“Nobody wants their this family reunion or vacation disrupted,” Chin-Hong said. “Those are reasons to just be a little bit smart at this time.”