A new COVID-19 variant, nicknamed Nimbus, is rising around the world — including in California — and known for giving “razor blade throat” symptoms.
Officially called NB.1.8.1, the variant was labeled a “variant under monitoring” by the World Health Organization on May 23, according to a recent report. That means it’s not currently a major threat; however, it’s spreading fast enough to raise flags. As of late April, it made up 10.7% of global COVID-19 samples, a jump from 2.5% just a month earlier.
The variant was first spotted in January and carries several genetic changes, particularly in the spike protein, the part of the virus that helps it infect human cells. Some of those changes might help it spread more easily or avoid the body’s immune response, especially in those who were previously infected or vaccinated.
“Every time you get a new strain, it always is a little bit more transmissible than what came before it,” Dr. Peter Chin-Hong, a UCSF infectious disease specialist, told SFGATE. “Just like a pop song is more catchy when it rises to the top of the charts. And this particular one, Nimbus, is not just proportionally higher right now in California, the speed at which it’s rising in the charts is also high … but it’s not more severe.”
Stanford’s Clinical Virology Laboratory confirmed one of the first cases of the variant in California on April 17 in the GISAID COVID-19 database, according to the San Francisco Chronicle. Although most infections in the U.S. are still caused by a related variant called LP.8.1 — a descendant of Omicron — Nimbus is rapidly gaining ground.
“The proportion of NB.1.8.1 sequenced from COVID-19 positive samples is rising,” the California Department of Public Health told SFGATE in a statement. State officials said the variant is currently growing faster than other strains and is being tracked closely through genomic sequencing and wastewater surveillance.
While wastewater levels appear to have stabilized in recent weeks, test positivity has slowly increased from 1.1% in March to 2.8% by June. Despite this, hospitalization rates remain low and steady, the agency said.
Reports of severe sore throat symptoms — described by some as feeling like swallowing shards of glass — have drawn attention in recent weeks, but Chin-Hong emphasized that this isn’t a new development.
“There’s always been a range of sore throats that people have had when they have COVID,” he said, “more frequently reported with Omicron than with, you know, pre-Omicron, and in fact, 70% of people have a sore throat reported with COVID.
“It is a good reminder that COVID isn’t always a walk in the park, even if you don’t go to the hospital. If you can, try not to get it. It’s going to help everyone out, right?”
San Francisco is currently experiencing low COVID-19 rates, according to the city’s Department of Public Health, but officials are encouraging residents to remain up to date on their vaccinations, especially with summer travel ramping up.
“The new NB.1.8.1 variant has begun to spread in the United States,” the department shared in a statement to SFGATE, noting that the current vaccine should be effective. “The currently available 2024-25 vaccine is expected to provide protection against it.”
Chin-Hong noted that the recent rise in Nimbus cases fits into a familiar seasonal pattern, one that has repeated each summer since the Omicron era began.
“The potential [of Nimbus spreading] is high. … It seems to be a summer bug as well as a winter bug,” he said, adding that last summer, COVID-19 levels in wastewater were much higher compared to winter.
He pointed to several factors fueling the uptick: Many people are past the six-month mark since their last infection or vaccination, increasing susceptibility; and with summer travel ramping up, there are more opportunities for the highly transmissible variant to spread.
Even if hospitalizations remain low, he cautioned that the virus still poses a risk to vulnerable groups and urged those who are older or immunocompromised to take precautions like masking and updating their vaccines. In the past three months ending June 7, 255 people have died in California from COVID, according to the Centers for Disease Control and Prevention’s provisional data.
“Particularly if you’re older … more than 50% [of people over 65] did not get their vaccine last year,” Chin-Hong said. “They would still be eligible for it for the summer.”
And while most people won’t get seriously ill, he emphasized that preventing infection still matters.
“Even if you’re not going to the hospital, which is most of the population, it’s still a drag” contract COVID-19, he said. “I’m not saying people have to panic, but be really COVID street smart.”
