Covid-19 cases, driven by the development of BA.2, are on the rise again in the United States



CNN

Covid-19 case numbers have begun to increase in the United States, and they are all caused by the Omigron subtype BA.2.

According to recent estimates by the U.S. Centers for Disease Control and Prevention, BA.2 was responsible for 86% of new Govt-19 cases nationwide last week.

In some ways, it feels like a familiar place. Again cases are on the rise. At least one big city is restoring its mask order. Broadway shows have canceled some shows.

But the reasons for the optimism remain.

Despite the complete acquisition of BA.2 from the other two circulating Omigron subtypes BA.1 and BA1.1, the number of hospital admissions in the US remains very low and continues to decline. Mortality is also steadily declining.

Although those numbers lag behind in case numbers, the United States has not seen a steep increase in epidemics. Whether that will happen is still an open question.

Even Dr. Anthony Fauci, director of the National Institute for Allergy and Infectious Diseases, has no idea what PA2 will do. As a nation, he says, the spread should be “less than our population or economy, our daily economy, workplaces and social life should not be disrupted, that is, it should be less than it is. A serious threat to the nation’s health.” He did not know if we had left the forest.

“We are definitely seeing the beginning of a new epidemic,” Fassi said. “It depends on how high we go in the uprising and whether it is associated with an increase in acute illness.

“I can’t tell you where we are now because we are changing,” he said.

Nationwide, Govt-19 cases are up 24% from where they were two weeks ago, and there are now an average of about 38,000 cases a day in the United States. This is an improvement from last week, perhaps because Florida recently reported a two-week backlog. Even so, owning one is still beyond the reach of the average person.

However, state-wise, the picture is quite mixed. Cases are on the rise in 25 states, down from 16 and are stable in the other nine states.

Cases are rapidly increasing in the Northeastern United States with the spread of BA.2.

On Monday, Philadelphia became the first major U.S. city to announce a return to indoor mask needs. Cases have risen 50% in the last 10 days, pushing the city over the threshold of triggering mask orders.

“I suspect this wave will be smaller than the one we saw in January,” Dr. Cheryl Pettigole, Philadelphia’s public health commissioner, said Monday.

“But if we wait to find and re-wear our masks, we will miss the opportunity to stop the wave.”

Several universities, including Johns Hopkins, American, George Washington and Georgetown, have re-established the interior mask.

New York City is reconsidering its mask requirements for preschool children, but as cases in the city increase, Mayor Eric Adams recently said that younger children will continue to need masks, and they will be hospitalized at higher rates during Omicron.

Beyond the number of cases, this may be a less reliable infection measure because test numbers have dropped, and corona virus levels in sewage often tell a promising story.

Sewage monitoring is considered a reliable warning of what is in the way. According to Biobot Analytics, a company that studies wastewater samples across the country, U.S. numbers are rising slightly, but one of the lowest levels seen since July.

The situation here with BA.2 seems to be different from that seen in the UK and Europe.

According to the variation-monitoring website Covariants.org, the Netherlands was nearing the peak of its BA.2 wave, when the sub-variant reached 83% of infections there in the second week of March. As Switzerland also approached its BA.2 peak, the subtype reached 80% of infections by mid-March. After a week-long decline, cases in the UK doubled from a low point on February 25 and soon reached the height of the BA.2 wave when the sub-variation between March 7 and March 21 caused 88% of cases.

The BA.2 experience in the United States seems to be similar to what happened in South Africa. In the second and third weeks of February, when BA.2 was responsible for 88% of the spread, cases pumped slightly, but continued to fall in March.

“As we have seen when Omigran first appeared, I was cautiously optimistic about PA2 due to the lack of rapid increase in cases,” said Pavithra Roy Chowdhury, who studies the spread of infectious diseases at the university. Washington Medical School.

He said the tidal wave of Omigran that hit the United States in the winter had left a lot of immunity in its wake. We are giving more vaccines and incentives to a country than ever before – however health officials say we can do even better with boosters.

Some are heeding that warning. The speed of vaccination has roughly doubled in the last two weeks as more and more people are seeking second boosters.

According to CDC data, an average of 502,000 vaccine doses were administered each day during the past week. On March 29, the CDC and the US Food and Drug Administration allowed a second booster shot for people 50 and over, from about 219,000 doses a day, although the CDC did not specifically count second boosters.

“This may illustrate our somewhat optimistic outlook compared to places like the UK, where there was a significant upsurge and it was associated with BA.2,” Raichhoudhury said.

During epidemics as a whole, health officials point to the UK as a precursor to things to come in the United States, but that kind of extrapolation can be difficult to do as people develop different types and immunity.

The tidal wave of cases caused by Omicron’s BA.1 variant peaked in January and then plummeted, with the UK seeing a second increase in cases and hospitals with BA.2. That wave peaked in late March, and since then, cases have been falling sharply.

Adam Kucharsky, an epidemiologist at the London School of Hygiene & Tropical Medicine, monitors epidemics and believes the BA.2 wave in the UK is low due to the timing of its booster campaign.

The UK began offering booster shots, or third vaccines, in mid – September, just days before the United States. But more people got them: in the UK, 68% of people over the age of 12 are eligible for the booster dose; According to the CDC, in the United States, that number is just 45%.

Many people who received a booster in the UK in September or October had higher antibody protection when Omigran arrived.

Antibodies are the first line of infection. They act quickly to prevent the virus from spreading throughout the body. Antibodies are high and decrease over the first few months of vaccination. But even after they are dropped, the body retains its immune memory for vaccines and is quickly ready to do more if it becomes infected.

Omicron was identified in late November, with many in the UK still within a higher safety window from their booster doses.

“I think we were lucky that the boosters provided a lot of protection in the short term,” Kuzharsky said.

Those who receive the latest boosters, even if they have PA1 disease, may not be aware of it because their symptoms are so mild. Kucharsky thinks they did not contribute to the spread, so the boosters did a good job of preventing the spread of Omigran throughout the UK during the winter.

However, fast forward three months, and many who received the recommended boosters passed their footage six months later. Studies show that antibody levels decrease four or five months after the third dose, so their protection against infection may be very low once BA.2 is exposed.

Now, Kucharsky says, with BA.2, even the motivated group was “mild, mild enough to detect symptoms or test positive” and counted as a case.

Whether the United States sees new cases from BA.2 depends on two things, Kucharzky said: the current immunity in the population and our behavior.

According to the CDC, half of those eligible for the booster dose in the United States receive one, and millions more are infected with Omigran, which provides some 95% of Americans with some protection against the corona virus.

But those who have lost their immunity over time may find a way to spread the virus as protection from their original two-dose vaccines has diminished or they became infected with the old variant a year or more ago.

“I think PA2 Vulnerability can be detected, which translates into development in cases, “Kuzharsky said.

But he insists there will be a lot depending on what Americans are doing now.

“I think the question is what’s going on in the meantime. [the subvariant]. But based on what we see in many countries in Europe, if there is an infection, it could translate into a growing epidemic because people do not have a booster or they had it a while ago, ”he said.

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