While the numbers and health risks are still low, the new “Cicada” strain of COVID-19 has been slowly — but heavily — mutating since it arrived at SFO last summer. Officials say it may be capable of evading immunity, and they warn that COVID typically spreads more rapidly in the summer months.

The variant was first identified in South Africa in late 2024 and reached the US at least by last June, when it was first detected in a traveler who landed at San Francisco International Airport from the Netherlands, according to the CDC. Since then, it’s been detected in at least 31 states and more than 30 countries, though overall prevalence remains low, as Today reports.

Nicknamed “Cicada” for its tendency to fade into the background before resurfacing, the variant has been traveling undetected behind more dominant strains for two years. According to NBC Bay Area, wastewater monitoring has picked up traces in the Bay Area, but not at significant levels so far.

Experts say the mutations of the Ciacada strain could help it sidestep existing immunity and potentially gain traction during the summer, as COVID transmission spiked during the summer months in 2024 and 2025, as SFist previously reported.

“This very mutated version could certainly make its rounds when we’re both immunologically more vulnerable and we get together during the summer,” said UCSF infectious disease specialist Dr. Peter Chin-Hong, per NBC Bay Area.

Researchers say the Cicada variant stands out for its extensive mutations, particularly in the spike protein — the part of the virus targeted by vaccines and prior immune responses, per Today. Those changes could make it harder for the immune system to recognize, potentially reducing protection from past infections or vaccinations, according to findings published in the CDC’s Morbidity and Mortality Weekly Report.

Even so, there’s no indication it causes more severe illness. “It’s not a more problematic strain than previous ones,” said Dr. Adolfo García-Sastre of Mount Sinai, pointing to data from countries where the variant is more widespread.

Estimates of its spread vary — CDC wastewater data put the variant at about 7% of samples nationwide in late March, while Stanford’s WastewaterSCAN project found it in roughly 20% of sequenced samples in early April. Reduced surveillance in recent years has made it harder to pin down its true prevalence, as Today reports.

The variant’s mutations have also reportedly raised questions about vaccine performance. Current COVID-19 shots, designed to target older strains, are still expected to protect against severe disease, though lab studies suggest they may be less effective against the Cicada strain. Health officials note vaccines can be updated seasonally to better match circulating variants.

Nevertheless, experts continue to recommend vaccination for reducing severe illness and limiting spread, particularly for older adults and people with underlying conditions.

Related: There’s a Scary New COVID Variant, and Stanford Scientists Say It’s Already in California

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