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A highly mutated COVID-19 strain is circulating in California — raising concerns that disease activity could rise heading into the summer. The emergence of the BA.3.2 strain, nicknamed “cicada,” comes amid broader uneasiness about COVID vaccination rates among seniors — who are especially susceptible to the virus — and whether complacency after back-to-back relatively quiet winters has left the elderly vulnerable. The “cicada” nickname refers to this subvariant’s apparent dormancy before it reemerged in 2025, akin to some periodically active insects of the same name.
The timing of the spread of the cicada subvariant also underscores that COVID has lately morphed into more of a summer disease in California. In fact, the summer peaks of COVID in 2024 and 2025 were worse than their respective winter peaks, according to the California Department of Public Health — a stark departure from the earlier years of the pandemic, when winter surges ripped through California with devastating regularity.
Instead it was the flu that was the dominant respiratory virus the last two winters, with this past season considered moderately severe.
“This cicada variant may be increasing just in time for what for COVID is more of a summer hit,” said Dr. Neil Silverman, director of the Infections in Pregnancy Program at the David Geffen School of Medicine at the University of California, Los Angeles. “COVID doesn’t seem to play by the same rules that influenza tends to play by, where its cycle is predictable.”
Dr. Peter Chin-Hong, a UC San Francisco infectious diseases expert, said cicada is “a different kind of variant that’s increasing. It looks so different from the other ones that have been circling since JN.1 came on board” in late 2023.
“My ears are perking up,” he said. In lab studies, the cicada subvariant efficiently evades immunity from a prior vaccination or infection, according to a report published by the U.S. Centers for Disease Control and Prevention. That raises the possibility of a seasonal increase in COVID-19, the researchers said.
“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.
During the 2024-25 respiratory virus season, there were an estimated 45,000 to 64,000 COVID deaths and 390,000 to 550,000 hospitalisations. A potential uptick is concerning as recent COVID vaccine coverage remains scant — even among the most vulnerable Californians. Statewide, just 28.7% of seniors age 65 and up have received at least one dose of the COVID vaccine that was updated in September.
The California Department of Public Health recommends that everyone ages 6 months and up should have access to the vaccine, and that those at higher risk of severe illness should get immunised — including older adults, pregnant women and infants and toddlers. The same goes for healthcare workers, residents of long-term care facilities and people who have household members at high risk.
People at higher risk for COVID-19, including seniors and those who are immunocompromised, should get two doses of the updated COVID-19 vaccination, spaced six months apart, state health officials said in a briefing to health professionals.
“To me, the biggest threat … is the low vaccination rate in seniors,” Chin-Hong said. “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 initially detected in South Africa in November 2024, and first found in the US in a sample given at San Francisco International Airport in June 2025 by an international traveler from the Netherlands. By that September, detection of the subvariant was increasing. In November, BA.3.2 was identified in a wastewater sample in Rhode Island; and among patients, the first detections of the new subvariant were found in three different states in December and early January.
As of February, the cicada subvariant has been reported in 23 countries, and has also been seen among airline passengers to the U.S. traveling from the United Kingdom, Japan and Kenya. Over the autumn and winter, about 30% of coronavirus samples analyzed in three European countries — Germany, the Netherlands and Denmark — were the Cicada subvariant, according to the Morbidity and Mortality Weekly Report. It’s not a surefire bet the cicada subvariant will bring a summer of misery, however. COVID wasn’t appreciably worse this past winter than in previous years in central Europe.
