What is the BA.2 sublineage of omicron?

Although BA.2 has been described as a “subvariant” of omicron, scientists point out it is quite different — as different from omicron as the delta variant is from the alpha variant , said Jeremy Luban, a virologist at the University of Massachusetts Medical School. There is no evidence BA.2 makes people sicker than its omicron progenitor, and experts say vaccines will continue to protect against severe outcomes from BA.2 as they have in cases involving other variants.

Is BA.2 sparking another surge of cases?

So far, no broad surge of new cases has emerged in the United States, despite upticks in several nations in Europe and Asia. There are so many variables at work when it comes to coronavirus transmission — including a population’s level of protection from vaccinations and prior infections, and its behavior, perhaps the hardest factor to predict or measure — that disease experts cannot say with confidence whether and when a new wave will materialize. If a surge of significant magnitude were to occur, it would be the sixth since the virus’s arrival in early 2020.

Where was the original version of omicron confirmed?

Omicron was first reported in late November, but its exact origin is still unknown. Scientists in South Africa confirmed on Nov. 25 that they had detected a worrying variant. Days later, other nations including the Netherlands said they had reviewed genetic sequencing data and found that the variant was already circulating within their borders at the same time as when South Africa raised the alarm. The World Health Organization soon listed it as a “variant of concern.” In South Africa, where official statistics show that more than 43 percent of the adult population is fully vaccinated, the variant spread rapidly. By Dec. 14, the positivity rate hit 34.9 percent . However, by late December, South Africa’s top infectious-disease scientist said that the country had passed the peak of new omicron cases . The first confirmed case in the United States was reported in California on Dec. 1, and within weeks, it had been detected in all 50 states . By late December, the seven-day daily average coronavirus case count in the United States had surpassed the delta-driven summer surge , Washington Post figures show. And, by the next month, the number of new daily cases had surpassed 700,000. But cases and hospitalizations have significantly declined. As of March 2, cases had dropped to about 75,000 per day, the CDC said , though data shows the virus is still circulating throughout communities in the United States.

What do we know about omicron?

Omicron’s genetic profile is unique compared with other circulating variants, meaning it represents a new lineage of the virus. It is distinct from other variants in another crucial way: There is a greater number of mutations. Omicron has more than 30 genetic changes in the spike protein, the part of the virus that binds to human cells and allows it to gain entry. Scientists were worried that those mutations would make omicron more transmissible, even among those with a natural or vaccine-acquired immune response — and they appear to have been right. Antibodies defeat the virus by targeting spike proteins, but changes that alter the structure can prevent them from binding as they usually do to neutralize the target. The omicron variant probably picked up genetic material from a virus that causes the common cold in humans, according to a preliminary study by researchers from Nference, a Cambridge, Mass.-based firm that analyzes biomedical information. Venky Soundararajan, a biological engineer who co-wrote the study, noted that as a virus evolves to become more transmissible, it generally “loses” traits that cause severe symptoms — although he said more analysis is needed. Studies have suggested that in many cases, omicron has caused less severe disease than previous variants — and may even be more likely to lead to asymptomatic infections . But because it is so contagious, the large number of infections could still result in a sizable number of severe cases, some experts have said. Although omicron appears to be more adept at evading antibodies, so far, data has suggested that the vaccines, particularly after a booster shot, still offer protection, namely against severe disease.

Why is it called omicron?

The World Health Organization named the B.1.1.529 variant omicron in the tradition of giving variants a Greek letter name. After the most recently named variant, mu, officials chose to skip the next letters available for variants: nu and xi. “Nu is too easily confounded with ‘new,’ and Xi was not used because it is a common surname,” the WHO said in a statement to The Washington Post. The agency’s “best practices for naming new diseases suggest avoiding ‘causing offense to any cultural, social, national, regional, professional or ethnic groups,’ ” the WHO noted.

What has been done to halt the spread of omicron?

The international response initially focused on two fronts: travel restrictions and encouraging more people to get vaccinated. Within days of the discovery of the variant, several countries began curbing flights to and from South Africa and its neighbors to try to slow omicron’s advance. The United States imposed restrictions on travelers from Botswana, Eswatini, Lesotho, Malawi, Mozambique, Namibia, South Africa and Zimbabwe, though they have since been lifted . Still, all inbound international travelers to the United States age 2 and older must show a negative coronavirus test result, with the test taken no more than one day before departure, regardless of nationality or vaccination status. Those who recently had covid-19 may alternatively show documentation that they tested positive no more than 90 days before departure — and have recovered. Health experts recommend getting tested at a testing center, even pharmacies and local health departments — but not emergency departments. Not only does this clog up emergency rooms for people who need them, but it also creates a risk of exposure to covid-19 — both for the person unnecessarily visiting the ER and for others who are waiting for care, said William Schaffner, medical director of the National Foundation for Infectious Diseases. President Biden also announced that the federal mask mandate requiring travelers to wear masks on planes, buses and in transportation hubs has been extended through March 18. The CDC’s new covid-19 community levels framework does not affect travel requirements at this time, including wearing masks on public transportation, according to the CDC. U.S. public health authorities have also re-upped efforts to get shots into arms, including boosters for those who have already been fully vaccinated. The CDC recently expanded its recommendation on booster shots, stating that people 12 and older “should” get a booster five months after the initial Pfizer-BioNTech vaccine series, and those 18 and older should get boosted five months after the initial Pfizer or Moderna series or two months after the Johnson & Johnson shot. And despite the recent relaxation of mask recommendations, federal health authorities still recommend that everyone age 2 and older wear a mask in indoor public spaces in areas where the covid-19 community level is high. In addition, the CDC said people should avoid crowds and poorly ventilated areas, wash hands frequently, and, when needed, get tested and isolate to protect others.

Do we know whether vaccines are effective against omicron?

Several studies have shown the Pfizer-BioNTech and Moderna vaccines remained highly effective at preventing the worst outcomes from omicron infections even as protection against mild illness waned. The nearly 17 million Americans who received the one-shot Johnson & Johnson coronavirus vaccine were less protected against serious illness and hospitalization. Studies also show that fully vaccinated individuals who received a booster shot had robust protection against the omicron variant. But officials worry about lags in getting Americans to sign up for booster shots, which were also shown to increase protection against omicron. More than 97 million people in the United States have gotten the extra shots, of 217 million who are fully vaccinated, according to the CDC as of March 28. In the first in-depth laboratory study on omicron, scientists in South Africa found that omicron was able to elude a great deal of the protection provided by disease-fighting antibodies. But the study, a preprint that has not yet been peer-reviewed, also said that previous infection followed by vaccination or a booster shot was likely to “confer protection from severe disease in Omicron infection,” suggesting boosters could be important. One recent study showed omicron-fighting antibodies persisted for four months after a third dose of the Pfizer-BioNTech vaccine, suggesting that a fourth shot may not be immediately necessary. And a similar study found that the Moderna booster remained effective against the variant in laboratory tests for at least six months. In the event that vaccines lose some of their punch, vaccine makers say they could also adjust their formulas relatively quickly to target omicron. Given the spread of omicron in South Africa, several experts have pointed to the need to vaccinate underserved countries to bolster the world’s protection from future, more-evasive variants. “I think vaccine equity is a really important issue,” said Linda Bauld, a professor of public health at the University of Edinburgh. She noted the low vaccination rates in many African countries and the fact that high prevalence of the virus means it can undergo many genetic changes each time it jumps between individuals. However, Bauld added, transmission of the coronavirus probably will not be eliminated even with a vaccine, as seen with the delta variant, with mutations ultimately able to “occur in any country.”

Does omicron cause severe illness, and do existing treatments work?

Current data indicates that the omicron variant causes milder cases of covid-19 than the delta variant — but scientists warn it can still be dangerous, especially to vulnerable populations, such as those who are not vaccinated. A major private study by Discovery Health, South Africa’s largest health insurer, published in December, found omicron appears to cause less severe illness than earlier coronavirus variants but is more resistant to the two-dose Pfizer-BioNTech vaccine widely. The scientists found that risk of hospital admissions among adults who developed covid-19 was 29 percent lower than in the initial pandemic wave that emerged March 2020. Two companies that have developed monoclonal antibodies, which are designed to prevent severe illness, recently announced contrasting findings on the potency of such therapies against omicron. Regeneron Pharmaceuticals said in a news release that data confirms its therapy, REGEN-COV, has “diminished potency” against omicron but remains useful against the delta variant, which is still the dominant strain in the U.S. At the same time, AstraZeneca said a lab study of Evusheld, its coronavirus antibody cocktail, found that the treatment “retained neutralizing activity” against omicron. U.S. public health officials began stockpiling a monoclonal antibody treatment called sotrovimab in December. Laboratory studies have shown that the intravenous infusion from Vir Biotechnology and GlaxoSmithKline will hold up against the new variant. Christine Armario, Lateshia Beachum, Amy Cheng, Silvia Foster-Frau, Ellen Francis, Carolyn Y. Johnson, Lesley Wroughton, Tim Bella, Sammy Westfall , William Booth and Lena H. Sun contributed to this report. Read more: Countries race to cut travel links with southern Africa, amid fears of omicron’s potential to spread Announcement of new virus variant alarms world, as stocks crash and flights are banned Dow plunges more than 900 points as new coronavirus variant sends global markets reeling

Health

What to know about the omicron variant and subvariant BA.2

A more transmissible subvariant, BA.2, has become the dominant strain in the United States as the omicron surge has waned. Those most at risk are the unvaccinated and older than 75

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Updated March 28, 2022 at 5:17 p.m. EDT|Published November 26, 2021 at 2:23 p.m. EST

The BA.2 “stealth” omicron variant is expected to soon become the dominant strain. Here is what you need to know about a possible new wave of infections. (Video: Brian Monroe, John Farrell/The Washington Post)

After emerging in November, the omicron variant spread rapidly across the globe because of mutations that allowed it to evade some of the immunity produced by vaccinations and previous infections. In midwinter, tens of millions of people in the United States, many of them fully vaccinated and boosted, were infected by omicron.

Now, a subvariant called BA.2, which has many mutations not seen in omicron, is posing a new threat and accounting for a swiftly growing share of cases in the United States, as it propels sharp case increases in Europe and Asia. Preliminary research suggests BA.2 is at least 30 percent more transmissible than omicron.

The Centers for Disease Control and Prevention estimated that, as of March 19, BA.2 accounted for 35 percent of new infections. The genomics company Helix, analyzing more current data, put its own estimate at 70 percent. Both estimates show a steady rise toward dominance of the subvariant.

The rise in BA.2 cases comes as federal health authorities have relaxed certain recommendations. On Feb. 25, the CDC updated its mask guidelines, which no longer recommend masking for most people in indoor public spaces in counties with low to medium levels of covid-19 community transmission and hospitalizations. Most of America is now classified at those lower levels. However, other prevention strategies, such as vaccinations, are still recommended.

Coronavirus: What you need to know

Where do things stand? See the latest covid numbers in the U.S. and across the world. In the U.S., pandemic trends have shifted and now White people are more likely to die from covid than Black people.

The state of public health: Conservative and libertarian forces have defanged much of the nation’s public health system through legislation and litigation as the world staggers into the fourth year of covid.

Grief and the pandemic: A Washington Post reporter covered the coronavirus — and then endured the death of her mother from covid-19. She offers a window into grief and resilience.

Would we shut down again? What will the United States do the next time a deadly virus comes knocking on the door?

Vaccines: The CDC recommends that everyone age 5 and older get an updated covid booster shot. New federal data shows adults who received the updated shots cut their risk of being hospitalized with covid-19 by 50 percent. Here’s guidance on when you should get the omicron booster and how vaccine efficacy could be affected by your prior infections.

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