Highly-mutated COVID strain spiking in California — here’s where clusters have formed

A new strain of COVID is rising in California with clusters detected in San Francisco and Kern County.

The “Cicada” strain is a highly mutated subvariant that has recently gained traction in California due to its ability to evade immunity from past infections and vaccinations.

It is arriving just as COVID-19 has increasingly behaved like a summer virus in California, with the last two years showing higher peaks in warmer months than in winter.

“This Cicada variant may be increasing just in time for what for COVID is more of a summer hit,” Dr. Neil Silverman, the director of the Infections in Pregnancy Program at the David Geffen School of Medicine at UCLA told the paper.

“COVID doesn’t seem to play by the same rules that influenza tends to play by, where its cycle is predictable.”

The nickname reflects the way the variant seemed to lie low before reappearing, similar to cicadas that emerge after periods of dormancy.

In contrast to earlier phases of the pandemic, recent winters have been dominated more by the flu, while COVID activity has shifted into the summer months.

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“Although widespread infection- and vaccine-conferred immunity have decreased rates of severe COVID-19 over time, the public health impact of COVID-19 is still considerable,” scientists recently wrote in the CDC’s Morbidity and Mortality Weekly Report.

State health officials advised that individuals at higher risk for COVID-19 — such as older adults and those with weakened immune systems — should receive two updated vaccine doses, given six months apart.

“To me, the biggest threat … is the low vaccination rate in seniors,” Dr. Peter Chin-Hong, a UC San Francisco infectious diseases expert , told the Times. “The landscape of divisiveness around vaccines is leading people to be confused and to think of COVID as being political when it’s not.”

The Cicada subvariant was first identified abroad in late 2024 and later detected in the United States through international travel.

Since then, it has appeared in multiple states and countries, with clusters identified through wastewater monitoring and traveler screenings, according to Alexandria Boehm, professor of civil and environmental engineering at Stanford University.

In California, traces of the variant have been found in sewage data, though overall levels remain relatively low so far.

Health experts say that while the variant has not yet been linked to more severe illness, its mutations make it distinct from earlier strains, raising concerns about how it could spread.

Current projections suggest a possible modest increase in cases later in the summer and early fall rather than a dramatic sudden surge.

Even so, vaccination rates remain a major concern, especially among older adults who are most vulnerable to severe outcomes. Fewer than one-third of California seniors have received the latest updated COVID shot, leaving a significant portion of the population at higher risk if cases rise.

Experts emphasize that vaccines continue to offer strong protection against severe illness and can also reduce the risk of long COVID. They warn that repeated infections can increase the chances of lingering symptoms, reinforcing the importance of staying up to date on vaccinations.

“The clouds are coming, and you might get a downpour, or it might just pass on. We don’t really know, but it just gives us some pause,” Chin-Hong said.

The COVID-19 virus emerged in late 2019, reached the U.S. on January 20, 2020, and has since caused over 1.1 million deaths in the U.S. and at least 7 million reported globally.

The SARS-CoV-2 has evolved through numerous variants since then.

According to the CDC, the virus spreads mainly through respiratory droplets and aerosols from breathing, talking, coughing, or sneezing — especially in crowded, poorly ventilated spaces—and can be transmitted even by people without symptoms.