By Brenda Goodman, Nation World News
The number of COVID-19 cases in the United States is beginning to rise, and nearly all of them are caused by the Omicron subvariant BA.2.
BA.2 caused 86% of new COVID-19 cases nationwide last week, according to the latest estimates from the US Centers for Disease Control and Prevention.
In some ways, it feels like a familiar place. Cases are on the rise again. At least one major city is restoring its facade mandate. Broadway shows have canceled some performances.
But there are still reasons for optimism.
Despite the near-complete acquisition of BA.2 from two other circulating Omicron subvariants, BA.1 and BA 1.1, US hospitalizations remain at record lows, and they continue to fall. The death toll continues.
Even though those numbers lag behind the number of cases, the US hasn’t seen a huge increase in infections. Whether this is likely to happen is still an open question.
Even Dr. Anthony Fauci, director of the National Institute of Allergy and Infectious Diseases, doesn’t know what a BA.2 will do. As a nation, transmission has to be reduced to a level that is “low enough that it does not disrupt our population or economy, our daily economic, workplace and social life, which means it must be low enough that Don’t it. A serious threat to the health of the nation,” he says. He doesn’t know if we are out of the woods.
“We are certainly seeing the beginning of a surge of new infections,” Fauci said. “It depends on how high we go in the surge, and it depends on whether the increase is linked to an increase in serious disease.
“I can’t say where we are right now, because we’re transitioning,” he said.
Regionally increasing cases
Across the country, Covid-19 cases have increased by 24% from where they were two weeks ago, and the US now averages about 38,000 cases a day. That’s a jump from last week, probably because Florida recently reported a two-week backlog. Still, it is one of the lowest daily rates since July.
State by state, however, the picture is more mixed. Cases are rising in 25 states, falling in 16 and stable in nine others.
Cases are rising rapidly in the Northeast, the region of the US with the highest BA.2 transmission.
On Monday, Philadelphia became the first major US city to announce the return of indoor mask requirements. Cases have climbed 50% in the past 10 days, pushing the city on the threshold of triggering a mask mandate.
“I suspect this wave will be smaller than the wave we saw in January,” Philadelphia Public Health Commissioner Dr. Cheryl Bettygole said Monday.
“But if we wait to detect it and put our masks back on, we will lose our chance to stop the wave.”
Several universities, including Johns Hopkins, American, George Washington and Georgetown, have also reinstated indoor masking.
New York City was reconsidering its mask requirements for preschoolers, but with cases rising in the city, Mayor Eric Adams recently said masks would continue to be required for the youngest children, compared to those in previous waves. The hospitalization rate was higher during Omicron in the U.S.
Beyond the case count, which may be a less reliable pandemic metric as testing numbers have declined, coronavirus levels in wastewater tell a largely reassuring story.
Wastewater monitoring is supposed to be a reliable warning of what is happening along the way. The US numbers are trending up slightly, but are still one of the lowest levels seen since July, according to Biobot Analytics, a company that analyzes wastewater samples from across the country.
Different countries, different stories
Here the position of BA.2 appears to be different from that observed in the UK and Europe.
According to the variant-tracking website Covariants.org, the Netherlands was at the peak of its BA.2 wave when the subvariant reached 83% of infections in the second week of March. Switzerland was also close to its BA.2 peak when the subvariant reached 80% of infections in mid-March. After falling for weeks, cases in the UK doubled from the low point on 25 February and would soon reach the height of the BA.2 wave, when the subvariant was causing 88% of cases there between 7 March and 21 March .
The BA.2 experience in the US looks a lot like it did in South Africa. In the second and third weeks of February, when BA.2 accounted for about 88% of transmission there, there was a slight jump in cases but then continued to decline in the month of March.
Pavitra Roychowdhury, who studies the spread of infectious diseases at the university, said, “I’ve been cautiously optimistic about BA.2 because it’s trends haven’t led to the rapid increase in cases, as we saw when Omicron. emerged for the first time.” Washington School of Medicine.
He said Omicron’s tidal wave has hit the US in winter and left much immune in its wake. We as a country are immunizing and promoting more than ever before – although health officials say we can do much better on boosters.
Some are heeding that warning. The pace of vaccination has nearly doubled in the past two weeks as more people are looking for second boosters.
According to CDC data, an average of about 502,000 vaccine doses have been given each day over the past week. This is up from about 219,000 doses a day as of March 29, when the CDC and the US Food and Drug Administration authorized a second booster shot for people 50 and older, although the CDC does not specifically count the second booster. doing.
“This may explain our somewhat more optimistic outlook compared to places like the UK, where there was a significant surge and it was associated with BA.2,” Roychowdhury said.
BA.2 in UK
Throughout the pandemic, health officials have pointed to the UK as a harbinger of things to come to the US, but it can be hard to extrapolate as populations develop different types and degrees of immunity.
After a wave of cases caused by Omicron’s BA.1 subvariant, which peaked in January and then fell, the UK saw a second increase in cases and hospitalizations with BA.2. The wave peaked in late March, and since then, there has been a steep decline in cases.
Adam Kucharsky, an epidemiologist at the London School of Hygiene and Tropical Medicine who tracks infectious disease outbreaks, believes the BA.2 wave in the UK is at least partly due to the timing of its booster campaign. The reason was
The UK began offering booster shots, or the third vaccine dose, in mid-September, just days before the US. But more people got them: In the UK, 68% of people over the age of 12 who are eligible for a booster dose have received one; According to the CDC, the number in the US is just 45%.
Many people in the UK who received a booster in September or October also had high antibody protection when it came to Omicron.
Antibodies are the first line of defense in infection. They act rapidly to stop the spread of the virus through the body. Antibodies are highest in the first few months after vaccination and decline over time. But even after they are released, the body retains its immune memory to vaccines and can quickly prepare to make more if infected.
Omicron was identified in late November, when many in the UK were still within the window of highest protection from their booster doses.
“I think we were lucky that the boosters provided, at least, quite a bit of protection,” Kucharsky said.
People who had recently had boosters had such good immunity that even if they became infected with BA.1, they might not have known because their symptoms were so mild. It was likely they weren’t contributing to transmission, Kucharsky thinks, so the boosters did a good job of containing Omicron’s massive outbreak in the UK over the winter.
Fast-forward three months, however, and many people receiving boosters as recommended were six months before their shots. Studies show that antibody levels decrease four or five months after the third dose, so their protection against infection was probably very low as BA.2 arrived on the scene.
And now, Kucharski says, with BA.2, even the enlarged group began to get “mild, mild symptoms or enough to detect it and test positive” and be treated as a case. began to be counted as
As the resistance decreased, BA.2 decreased
Whether the US will see a new wave of cases from BA.2 will depend a lot on two things, Kucharsky said: the current level of immunity in the population and our behavior.
According to the CDC, nearly half of those eligible for a booster dose in the US had one, and millions of people were infected with Omicron, giving an estimated 95% of Americans some degree of protection against the coronavirus.
But for people who have lost their immunity over time because protection from their original two-dose vaccination has decreased or because they were infected with an older version a year or more ago, the virus may find a way to spread. Is.
“I think if BA.2 can find sensitivity, it will translate into an increase in cases,” Kucharsky said.
But he stressed that a lot will depend on what Americans do now.
“I think the question is, what happens in the meantime, if there’s actually a booster campaign and other things that can be offset [the subvariant], But I think based on what we’re seeing a lot of countries in Europe, if there’s sensitivity, either people didn’t have boosters or they had some time ago, it could translate into a growing epidemic , “They said.
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