Notorious 'winter vomiting bug' rising in California. A new norovirus strain could make it worse

The dreaded norovirus — the “vomiting bug” that often causes tummy flu symptoms — is climbing again successful California, and doctors pass that a caller subvariant could marque adjacent much radical sick this season.

In L.A. County, concentrations of norovirus are already connected the emergence successful wastewater, indicating accrued circulation of the disease, the section Department of Public Health told the Los Angeles Times.

Norovirus levels are expanding crossed California, and the emergence is particularly notable successful the San Francisco Bay Area and L.A., according to the California Department of Public Health.

And the complaint astatine which norovirus tests are confirming corruption is rising nationally and successful the Western U.S. For the week that ended Nov. 22, the trial positivity complaint nationally was 11.69%, up from 8.66% 2 months earlier. In the West, it was adjacent worse: 14.08%, up from 9.59%, according to the U.S. Centers for Disease Control and Prevention.

Norovirus is extraordinarily contagious, and is America’s starring origin of vomiting and diarrhea, according to the CDC. Outbreaks typically hap successful the cooler months betwixt November and April.

Clouding the representation is the caller emergence of a caller norovirus strain — GII.17. Such a improvement tin effect successful 50% much norovirus unwellness than typical, the CDC says.

“If your immune strategy isn’t utilized to thing that comes around, a batch of radical get infected,” said Dr. Peter Chin-Hong, an infectious diseases adept astatine UC San Francisco.

During the 2024-25 wintertime season, GII.17 overthrew the erstwhile ascendant norovirus strain, GII.4, that had been liable for much than fractional of nationalist norovirus outbreaks implicit the preceding decade. The ancestor of the GII.17 strain astir apt came from a subvariant that triggered an outbreak successful Romania successful 2021, according to CDC scientists.

GII.17 vaulted successful prominence during past winter’s norovirus surge and was yet liable for astir 75% of outbreaks of the illness nationally.

The strain’s emergence coincided with a peculiarly atrocious twelvemonth for norovirus, 1 that started unusually aboriginal successful October 2024, peaked earlier than mean the pursuing January and stretched into the summer, according to CDC scientists penning successful the diary Emerging Infectious Diseases.

During the 3 anterior seasons, erstwhile GII.4 was dominant, norovirus enactment had been comparatively stable, Chin-Hong said.

Norovirus tin origin important disruptions — arsenic galore parents cognize each excessively well. An simple schoolhouse successful Massachusetts was forced to cancel each classes connected Thursday and Friday due to the fact that of the “high measurement of tummy unwellness cases,” which was suspected to beryllium driven by norovirus.

More than 130 students astatine Roberts Elementary School successful Medford, Mass., were absent Wednesday, and administrators said determination astir apt wouldn’t beryllium a “reasonable fig of students and staff” to resume classes Friday. A institution was hired to execute a heavy cleanable of the school’s classrooms, doorknobs and room equipment.

Some places successful California, however, aren’t seeing large norovirus enactment truthful acold this season. Statewide, portion norovirus levels successful wastewater are increasing, they inactive stay low, the California Department of Public Health said.

There person been 32 lab-confirmed norovirus outbreaks reported to the California Department of Public Health truthful acold this year. Last year, determination were 69.

Officials caution the numbers don’t needfully bespeak however atrocious norovirus is successful a peculiar year, arsenic galore outbreaks are not lab-confirmed, and an outbreak tin impact either a tiny oregon ample fig of people.

Between Aug. 1 and Nov. 13, determination were 153 norovirus outbreaks publically reported nationally, according to the CDC. During the aforesaid play past year, determination were 235.

UCLA hasn’t reported an summation successful the fig of norovirus tests ordered, nor has it seen a important summation successful trial positivity rates. Chin-Hong said helium likewise hasn’t seen a large summation astatine UC San Francisco.

“Things are comparatively inactive unchangeable clinically successful California, but I deliberation it’s conscionable immoderate magnitude of clip earlier it comes here,” Chin-Hong said.

In a emblematic year, norovirus causes 2.27 cardinal outpatient session visits, mostly young children; 465,000 exigency section visits, 109,000 hospitalizations, and 900 deaths, mostly among seniors property 65 and older.

People with terrible ongoing vomiting, profound diarrhea and dehydration whitethorn request to question aesculapian attraction to get hydration intravenously.

“Children who are dehydrated whitethorn outcry with fewer oregon nary tears and beryllium unusually sleepy oregon fussy,” the CDC says. Sports drinks tin assistance with mild dehydration, but what whitethorn beryllium much adjuvant are oral rehydration fluids that tin beryllium bought implicit the counter.

Children nether the property of 5 and adults 85 and older are astir apt to request to sojourn an exigency country oregon session due to the fact that of norovirus, and should not hesitate to question care, experts say.

“Everyone’s astatine risk, but the radical who you interest about, the ones that we spot successful the hospital, are the precise young and precise old,” Chin-Hong said.

Those astatine highest hazard are babies, due to the fact that it doesn’t instrumentality overmuch to origin perchance superior problems. Newborns are astatine hazard for necrotizing enterocolitis, a life-threatening inflammation of the intestine that virtually lone affects caller babies, according to the National Library of Medicine.

Whereas steadfast radical mostly wide the microorganism successful 1 to 3 days, immune-compromised individuals tin proceed to person diarrhea for a agelong clip “because their body’s immune strategy can’t neutralize the microorganism arsenic effectively,” Chin-Hong said.

The main mode radical get norovirus is by accidentally drinking h2o oregon eating nutrient contaminated with fecal matter, oregon touching a contaminated aboveground and past placing their fingers successful their mouths.

People usually make symptoms 12 to 48 hours aft they’re exposed to the virus.

Hand sanitizer does not enactment good against norovirus — meaning that due handwashing is vital, experts say.

People should lather their hands with soap and scrub for astatine slightest 20 seconds, including the backmost of their hands, betwixt their fingers and nether their nails, earlier rinsing and drying, the CDC says.

One adjuvant mode to support way of clip is to hum the “Happy Birthday” opus from opening to extremity twice, the CDC says. Chin-Hong says his favourite is the chorus of Kelly Clarkson’s “Since U Been Gone.”

If you’re surviving with idiosyncratic with norovirus, “you truly person to cleanable surfaces and worldly if they’re touching it,” Chin-Hong said. Contamination is shockingly easy. Even conscionable breathing retired small saliva droplets connected nutrient that is aboriginal consumed by idiosyncratic other tin dispersed infection.

Throw retired nutrient that mightiness beryllium contaminated with norovirus, the CDC says. Noroviruses are comparatively resistant to vigor and tin past temperatures arsenic precocious arsenic 145 degrees.

Norovirus is truthful contagious that adjacent conscionable 10 viral particles are capable to origin infection. By contrast, it takes ingesting thousands of salmonella particles to get sick from that bacterium.

People are astir contagious erstwhile they are sick with norovirus — but they tin inactive beryllium infectious adjacent aft they consciousness better, the CDC says.

The CDC advises staying location for 48 hours aft infection. Some studies person adjacent shown that “you tin inactive dispersed norovirus for 2 weeks oregon much aft you consciousness better,” according to the CDC.

The CDC besides recommends washing laundry successful blistery water.

Besides schools, different places wherever norovirus tin dispersed rapidly are cruise ships, day-care centers and prisons, Chin-Hong said.

The astir caller norovirus outbreak connected a cruise vessel reported by the CDC is connected the vessel AIDAdiva, which acceptable sail connected Nov. 10 from Germany. Out of 2,007 passengers connected board, 4.8% person reported being ill. The outbreak was archetypal reported connected Nov. 30 pursuing stops that period astatine the Isle of Portland, England; Halifax, Canada; Boston; New York City; Charleston, S.C.; and Miami.

According to CruiseMapper, the vessel was acceptable to marque stops successful Puerto Vallarta connected Saturday, San Diego connected Tuesday, Los Angeles connected Wednesday, Santa Barbara connected Thursday and San Francisco betwixt Dec. 19-21.