U.S. Reports Its 1st Omicron Case, in a California Traveler

WASHINGTON — The Omicron coronavirus variant was reported successful the United States for the archetypal clip connected Wednesday successful a traveler who had been successful South Africa, arsenic scientists astir the satellite survey whether the variant is much transmissible oregon virulent than its predecessors.

The patient, a nonmigratory of San Francisco, is successful isolation, and assertive interaction tracing is underway, the Centers for Disease Control and Prevention said successful a statement. The idiosyncratic was afloat vaccinated, though without a booster shot, and was displaying mild symptoms that were improving, the bureau said.

The find prompted the Biden medication to renew calls for everyone to get afloat vaccinated and, if eligible, person a booster. It besides came arsenic the C.D.C. asked airlines for the names and interaction accusation of each passengers who had boarded flights bound for the United States since Nov. 29 and who had been successful confederate Africa successful the past 2 weeks.

The World Health Organization has warned that the hazard posed by the variant, which was archetypal identified successful South Africa connected Thursday, is “very high.” More than 20 countries person detected the variant.

California wellness officials said the authorities was expanding coronavirus investigating astatine airports, focusing connected arrivals from countries identified by the C.D.C. arsenic imaginable sources of the variant. Gov. Gavin Newsom said that California would not beryllium intensifying nationalist wellness restrictions, astatine slightest successful the abbreviated term, but that “we should presume that it’s successful different states arsenic well.”

“There is nary crushed to panic, but we should stay vigilant,” helium said successful a statement. “The champion happening we tin bash is to get vaccinated if you haven’t already, get your booster, and deterioration your disguise indoors. As we proceed to larn much astir this variant, get tested if you person symptoms, and enactment location if you’re sick.”

On Thursday, President Biden is expected to denote ways the authorities volition ramp up its combat against the microorganism during the wintertime months, including tougher planetary question restrictions and efforts to accelerate vaccine and booster availability.

Answers astir whether Omicron is much contagious oregon deadly stay elusive arsenic scientists astir the globe contention to representation its attributes — including much mutations than the Delta variant — and question to find whether the vaccines volition beryllium effectual successful protecting radical from corruption oregon superior hospitalization. Officials successful South Africa person said that they bash not cognize of immoderate deaths associated with the variant, but wellness experts accidental it is excessively aboriginal to measure its existent dangers.

Still, Omicron’s emergence during the vacation season, arsenic Americans prepared to stitchery with relatives, raised the grim imaginable of yet different surge successful a pandemic that has severely tested the patience of a weary public, caused unparalleled economical harm and stoked governmental division.

Speaking to reporters soon aft the variant’s find was announced, Dr. Anthony S. Fauci, the president’s apical aesculapian adviser, expressed optimism that the United States would yet look from the grip of the pandemic.

“This volition end,” helium said. “I committedness you that this volition end.”

Public wellness officials astir the satellite person said for days that they expect the new, mutated signifier of the microorganism volition rapidly find its mode to the United States contempt the imposition of a travel prohibition by the Biden administration and other governments connected planetary travelers from 8 confederate African nations precocious past month.

Scientific confirmation of the variant’s beingness successful the United States was nevertheless a jolt to Mr. Biden’s efforts to marque bully connected his run committedness to bring the pandemic to a swift and conclusive end. At the White House connected Wednesday, helium said that “we’re learning much each azygous day” and vowed that the medication would “fight this variant with subject and speed, not chaos and confusion.”

Shortly afterward, Dr. Fauci told reporters that confirmation of the caller variant successful the United States should transportation unvaccinated Americans to get shots immediately.

“We person 60 cardinal radical successful this state who are not vaccinated who are eligible to beryllium vaccinated,” helium said. “Let’s get them vaccinated. Let’s get the radical vaccinated, boosted. Let’s get the children vaccinated.”

Dr. Fauci besides urged caution, saying determination was overmuch that wellness officials did not cognize astir the caller variant.

“There’s a batch of accusation that is present evolving,” helium said.

Scientists person said that Omicron carries much than 50 familial mutations that successful mentation whitethorn marque it much contagious and little susceptible to the body’s immune defenses than erstwhile variants. More than 30 of the mutations are successful the virus’s spike, a macromolecule connected its surface. Vaccines bid the body’s immune defenses to people and onslaught these spikes.

In California, Mr. Newsom said the infected idiosyncratic had not been hospitalized, and different radical the idiosyncratic came successful interaction with person not, astatine this point, tested positive. The politician said the diligent traveled from South Africa, landed successful the United States connected Nov. 22 and started feeling mild symptoms connected Nov. 25. The idiosyncratic was tested for the coronavirus connected Nov. 28 and received a affirmative effect a time later.

In a day, scientists astatine the University of California, San Francisco, had determined that it was the Omicron variant.

The idiosyncratic had received 2 doses of the Moderna vaccine but was wrong the six-month model of its effectiveness and had not received a booster, Mr. Newsom said.

Mayor London N. Breed of San Francisco said successful a connection that the metropolis had “one of the highest vaccination rates and lowest decease rates successful the state due to the fact that of the actions our residents person taken from the opening of this pandemic to support each different safe.”

The city’s wellness director, Dr. Grant Colfax, added that “we are inactive learning astir the Omicron variant, but we are not backmost to quadrate 1 with this disease.”

About 79 percent of California residents person received astatine slightest 1 dose of a coronavirus vaccine. Cases and hospitalizations person mostly been trending downward aft a summertime summation driven mostly by the Delta variant.

In the Bay Area, wherever counties person immoderate of the highest vaccination rates successful the state, longstanding disguise mandates had precocious been relaxed oregon lifted arsenic the dispersed of the microorganism slowed. Local governments successful the authorities person begun to necessitate businesses to verify vaccination presumption for entry, and much workers person been required to get their shots — a inclination that officials person credited with helping to dilatory the spread.

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Throughout the pandemic, San Francisco County has avoided the situation levels that affected immoderate of the state’s different cities, similar Los Angeles, arsenic residents enthusiastically abided by restrictions, wore masks and got vaccinated. Seventy-seven percent of the county’s residents are afloat vaccinated, according to its Department of Public Health.

Dr. Bob M. Wachter, the president of the section of medicine astatine U.C.S.F., said that the lawsuit would not beryllium the past successful California. But for now, helium said, “I’m not changing my behaviour immoderate based connected a azygous oregon a fistful of cases.”

After quality of the variant’s dispersed successful South Africa, countries astir the satellite curtailed aerial question to and from the portion — measures that officials determination described arsenic unduly punitive, particularly successful airy of the information that Western countries had failed to deliver capable vaccines and logistical enactment to the continent.

Still, the C.D.C. volition toughen requirements for screenings and coronavirus testing, asking planetary travelers to supply a antagonistic effect taken wrong 24 hours earlier departure. Mr. Biden plans to denote the move, arsenic good arsenic an extension until mid-March of a disguise requirement connected airplanes and nationalist transit and astatine airports and transit stations, arsenic portion of his broader strategy, a idiosyncratic acquainted with the determination said connected Wednesday night.

Though the bureau has yet to denote immoderate changes, travelers were near scrambling for pre-emptive tests and preservation changes.

“It’s a shame, due to the fact that question conscionable opened up again,” said Giritharan Sripathy, who was scheduled to alert to New York from London connected Thursday.

Dutch officials said connected Tuesday that they had identified cases of the variant a week earlier Friday, erstwhile 13 passengers who arrived connected flights from South Africa tested affirmative for it, signaling that Omicron was already contiguous successful the Netherlands.

In South Africa, the variant accounts for astir of the caller regular cases reported successful the nation’s astir populous province, Gauteng, which is location to immoderate 15 cardinal radical and the cities of Johannesburg and Pretoria.

At the White House connected Wednesday, Dr. Fauci said helium was “not truthful sure” that caller investigating requirements for planetary travelers, which medication officials are presently weighing, would person helped drawback the lawsuit earlier. The diligent had taken a trial instantly aft opening to acquisition what helium described arsenic mild symptoms.

Dr. Fauci added that it was imaginable that the national authorities could alteration its explanation of “fully vaccinated” to necessitate planetary travelers to person received booster shots earlier entering the United States.

Asked if Americans should consciousness escaped to be vacation parties and portion beverages unmasked, helium said it depended connected the size of the gathering.

“In a concern with a vacation season, indoor-type settings with household that you cognize is vaccinated, radical that you know, you tin consciousness harmless with not wearing a disguise and having a dinner, having a reception,” Dr. Fauci said. But successful larger nationalist settings wherever it is unclear if everyone is vaccinated, helium said, radical should deterioration masks but to devour oregon drink.

Michael D. Shear reported from Washington, Shawn Hubler from Sacramento, and Roni Caryn Rabin from New York. Reporting was contributed by Jim Tankersley and Sheryl Gay Stolberg from Washington, Jill Cowan from Los Angeles, and Aina J. Khan from London.