The Omicron subvariants BA.4 and BA.5 have together become dominant in the U.S., the C.D.C. estimates.

According to the report, the rapid march across the United States continued, with the Omicron submutants known as BA.4 and BA.5 together becoming predominant in the new coronavirus cases. New quote From the Centers for Disease Control and Prevention on Tuesday.

As of the week ending on Saturday, BA.4 accounted for 15.7% of new cases, BA.5 accounted for 36.6%, accounting for about 52% of new cases in the United States, experts say It should increase in the week. ..

The statistics released on Tuesday morning are based on modeling and may be revised as more data comes in. This happened in late December, when agency estimates deviated from the norm.

An independent advisor to the Food and Drug Administration met on Tuesday in a booster shot for Americans that could better match some versions of Omicron, even if the virus could evolve again by the fall. Released to consider updating the vaccine.

Less than six months after BA.4 and BA.5 were first detected in South Africa, two subvariants in the United States were two early Omicrons, including BA.2, which had been popular for some time. It looked like I was overtaking a subvariant. The beginning of this spring. The CDC estimates that as of the week to June 18, another BA.2.12.1 was dominant alone. After Omicron arrived in the United States, it sent a surge in cases during the winter. Prior to that, the delta type had prevailed in the United States since early summer.

BA.4 and BA.5 show the quality of escape artists who can avoid some of the antibodies produced after coronavirus vaccination and infection. This includes infections caused by previous versions of Omicron. It may explain why these subvariants spread even faster than the other subvariants in the Omicron family. However, there is still little evidence that they cause more serious illnesses.

Subspecies of BA.4 and BA.5 have been detected worldwide, and the number of cases surged in South Africa in the spring, despite the pre-existing immunity to the virus. The waves were not as high as the early waves in South Africa and the death toll did not increase so rapidly.South Africa last week Abolished the rule I needed a mask in an indoor public space.

That pattern seems to have been maintained in the United States so far.

According to the New York Times database, an average of more than 100,000 new coronavirus cases have been reported daily in the United States over the past few weeks. This number only captures a portion of the actual number. Many infectious diseases are not counted in official reports. Some scientists estimate that the current wave of cases is the second largest in the pandemic.

As of Monday, US hospitalizations have increased by 6% over the past two weeks, averaging over 31,000 a day, according to federal data. On average, new deaths are less than 400 per day, according to data from state and local health agencies. This is just a small part of the thousands that are seen daily during the peak of Omicron in winter.

“But in my opinion, there are still too many 250 deaths per day,” said CDC Director Dr. Rochelle Walensky. Said last week In Aspen, Colorado, “The dead we see are generally either the elderly, the frail, many comorbidities, vaccinated, or unvaccinated. “

Many Americans with risk factors said they felt ignored and abandoned because their government and neighbors wanted a return to normal.

As always, the spread of the virus is a regional issue. In the northeast and midwest, known cases have declined for several weeks, while in the south and west, cases have increased.

Public health regulations continue to be lifted nationwide, with the indoor mask mandate in Alameda County, the second most populous county in the San Francisco Bay Area, ending on Saturday. In New York City, Broadway theaters (except one) have abolished the mask requirement from Friday. Even the long-standing requirement to test the coronavirus before flying from abroad to the United States has been withdrawn this month.

The recent availability of vaccines for children aged 6 months to 5 years has been a welcome development for many parents and day care centers, but experts say that children are changing the overall trajectory of the pandemic in the United States. We do not expect the availability of dosages.

The natural decline in vaccine protection against infection, along with the antigenicity of BA.4 and BA.5, may explain why these submutants were able to spread rapidly. It also brought urgency to the development of boosters targeting Omicron. Vaccine makers have been competing to develop these, but they are based on previous versions of Omicron and it was not yet clear how well they could protect against BA.4 and BA.5 infections. ..

Reserve Evidence from laboratory studies Unvaccinated people infected with the original version of Omicron, known as BA.1, suggest that they can easily be re-infected with BA.4 or BA.5. Studies suggest that vaccinated people are more likely to be somewhat successful.

But as the virus evolves, no one knows if a modified vaccine can become obsolete before it becomes available.

“What we don’t know is what will happen with the new vaccine in the fall,” Dr. Warensky said while in Aspen. “I think we need more vaccines.”