A highly mutated strain of COVID-19 is circulating in California – raising concerns that disease activity could increase as summer approaches.
The emergence of the BA.3.2 strain, nicknamed “Cicada,” comes amid widespread uneasiness about COVID vaccination rates among the elderly – who are most vulnerable to the virus – and whether a lull after a relatively peaceful winter has left the elderly at risk. The nickname “Cicada” refers to the stay of this subspecies before it reappears in 2025, similar to the periodic insects of the same name.
The timing of the spread of the Cicada subvariant also emphasizes that COVID has recently evolved into a summer disease in California. In fact, the summer peaks of COVID in 2024 and 2025 were worse than their winter peaks, according to the California Department of Public Health — from earlier years of the epidemic, when winters hit California with devastating regularity.
Instead it was the flu that was a major respiratory virus the past two winters, this past season is considered moderately severe.
“This variant of Cicada is likely to grow at the right time of what is the most popular COVID in the summer,” said Dr. Neil Silverman, director of the Infections in Pregnancy Program at the David Geffen School of Medicine at UCLA. “COVID doesn’t seem to play by the same rules that the flu tends to play by, where its cycle is predictable.”
Dr. Peter Chin-Hong, an infectious disease expert at UC San Francisco, said the Cicada “is a different species that is emerging. It looks very different from the others that have been circulating since JN.1 arrived” in late 2023.
“My ears are pierced,” he said.
In laboratory studies, the Cicada subvariant effectively avoids vaccination or previous infection, according to a report published by the US 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-provided vaccinations – have reduced the rates of severe COVID-19 over time, the public health impact of COVID-19 remains significant,” scientists recently wrote in the CDC’s Morbidity and Mortality Weekly Report.
During the 2024-25 respiratory virus season, there are an estimated 45,000 to 64,000 COVID deaths and 390,000 to 550,000 hospitalizations.
What’s more likely is that recent vaccination coverage for COVID remains low — even among the most vulnerable Californians. Nationwide, only 28.7% of adults age 65 and older received at least one dose of the updated COVID vaccine in September.
The California Department of Public Health recommends that everyone 6 months of age and older should be able to get the vaccine, and that those at high risk of severe illness should be vaccinated — including older adults, pregnant women and infants and toddlers. The same goes for health care workers, residents of long-term care facilities and people with high-risk household members.
People at high risk for COVID-19, including the elderly and those with weakened immune systems, should receive two doses of the updated COVID-19 vaccine, six months apart, state health officials said at a health conference.
“For me, the biggest threat … is the low vaccination rate among the elderly,” Chin-Hong said. “The divisive nature of vaccines is leading people to get confused and think of COVID as political when it’s not.”
The Cicada subvariant was first detected in South Africa in November 2024, and was first detected in the US in a sample provided at San Francisco International Airport in June 2025 by an international traveler from the Netherlands.
That September, subvariant detection increased. In November, BA.3.2 was identified in a Rhode Island wastewater sample; and among patients, the first detection of the new subvariant was found in three different states in December and early January.
As of February, the Cicada subvariant has been reported in 23 countries, and has been seen among US-bound airline passengers traveling from the United Kingdom, Japan and Kenya. In autumn and winter, about 30 percent of the coronavirus samples analyzed in three European countries – Germany, the Netherlands and Denmark – were of the Cicada subvariant, according to the Morbidity and Mortality Weekly Report.
It’s not a sure bet that the Cicada subvariant will deliver a summer of misery, however. COVID was worse this past winter than in previous years in central Europe.
According to the California Department of Public Health, the Cicada subvariant remains at low levels in the state’s wastewater, and there have been no reports of increased severity of illness among those infected. It is also not meant to be the fastest growing variant, or the dominant one.
The last time the Cicada subvariant was detected in one public database, it represented about 5% of the samples identified in American wastewater in the week of March 28, according to Alexandria Boehm, a professor of civil and environmental engineering at Stanford University and the principal investigator of WastewaterSCAN, which monitors sewage to track the presence of infectious diseases.
In the first week of April, however, the Cicada subvariant was not detected, and all samples were of another type of COVID, XFG, according to Boehm.
It is worth noting that the concentration of the coronavirus in the wastewater was very low and, as a result, “it is difficult to obtain high-quality sequences with high confidence,” said Boehm.
In slides prepared for a recent forum of medical professionals, California health officials are predicting a possible wave of COVID in late summer and early fall.
Chin-Hong compared it to a weather report.
“Clouds are coming, you may get rain, or it may just pass.
Chin-Hong urged seniors who have not received the COVID vaccine in the past 12 months to do so. “Getting it once a year as a senior is going to be really important,” she said.
Data continues to show that the COVID vaccines are safe and effective, and protect both pregnant women — who are at risk of more severe disease if they are infected with the virus — and their newborns, Silverman said. Of infants up to 6 months of age hospitalized with COVID, nearly 90% were born to women who did not have a record of vaccination against COVID during pregnancy, according to a report published by the CDC.
Getting vaccinated also lowers the risk of prolonged COVID, “and the more times you get a COVID infection, the more likely you are to have prolonged COVID,” Silverman said.
“Covid is still here. People can’t really take comfort in the fact that we didn’t have an operation this past winter. And we need to anticipate that this variant could be a problem in the summer and early fall,” Silverman said.
