What We Know About the ‘Secret’ BA.2 Omicron Variant


As the Omicron coronavirus surge wanes, researchers keep an eye out for a highly contagious disease. Subvariant known as BA.2. While it doesn’t appear to have the capacity to drive a large wave of new infections, the variant could potentially slow the current decline in Covid cases and make treatments more difficult.

Here’s what we know so far about BA.2.

Scientists first discovered Omicron variant In November it quickly became clear that the viral lineage already existed as three genetically distinct varieties. Each branch of the Omicron had its own unique mutations. The most common at that time was BA.1, which spread rapidly around the world. BA.1 was almost entirely responsible for the record-breaking increase in cases this winter.

At first, BA.1 was a thousand times more common than BA.2. But in early 2022, BA.2 began to be found in a larger proportion of new infections.

All versions of Omicron are highly contagious, so the variant quickly outpaced earlier forms of the coronavirus like Delta. But a number of studies have found that BA.2 is even more contagious than BA.1.

Inside Denmarkfor example, the scientists studied the spread of both subvariables in homes. They found that people infected with BA.2 were significantly more likely to transmit BA.1 to people they shared a home with. Inside BritainThe researchers found that, on average, it takes less time for someone with BA.2 to infect another person, which speeds its spread across communities.

By early 2022, BA.2 was growing more common in several countries. With Februarybecame dominant worldwide, pushing down the once dominant BA.1. Centers for Disease Control and Prevention in the United States estimated BA.2 rose from 1 percent in early February to 11 percent in early March. It may soon become dominant in this country as well.

But that doesn’t mean that Americans are embarking on a new wave of BA.2 infecting many new people. As BA.2 became more common in the United States, the overall number of new cases dropped by nearly 95 percent. The number of new cases per day has decreased worldwide. my love What they are at their peak in late January.

As many countries relax their protections against the spread of Covid, it could make it easier for BA.2 to deliver a new surge in cases. March 10 report British researchers suggest it could be out there right now.

But there are several reasons why epidemiologists doubt that BA.2 will cause a major new surge.

One of the most striking features of the Omicron was its ability to partially evade the protection of vaccines. “Breakthrough” infections have become more common, helping to bring the increase in cases to a record high. However, vaccines continued to protect people, especially those who were supported, against severe illness. Vaccines remained throughout the Omicron surge high impact Against hospitalization.

British health authorities compared the effectiveness of vaccines against BA.1 and BA.2 infections. they have to create small difference between the two subvariables. And in both, the booster vaccine provides very strong protection against infection and very strong protection against hospitalization.

When the Omicron first appeared, scientists were surprised to see how effectively it was able to evade the immunity produced by infections with its earlier variants. This is because the virus has mutations that change its surface and make it harder for antibodies against earlier variants to stick to it.

Because BA.2 carries a number of unique mutations that distinguish it from BA.1, the researchers wondered if it could pass immunity from BA.1 infections. he is the situation does not seem so. world Health Organization said That infection with BA.1 provides strong protection against infection with BA.2.

The Omicron variant proved to be a paradox: It was highly contagious, but an individual infection was, on average, less likely to cause a serious case of Covid than infections from the Delta variant. This has resulted in many people getting mild Omicron infections. However, this did not mean that the Omicron surge was “mild”. As more people are infected than ever before, it has led to a staggering number of hospitalizations and deaths.

Research on the Omicron has uncovered several reasons for its reduced severity. Vaccines and infections with earlier variants have given many people immune defense that has prevented Covid from spiraling out of control. Omicron also proved to be less severe than other variants and less damage to the lungs.

Similar experiments with BA.2 are in progress. Japanese researchers infecting hamsters with two variants to create that BA.2 causes more severe disease. But it’s not clear how good a hamster model is for humans. British researchers to create BA.2 infection does not carry a higher risk of hospitalization than BA.1.

such as BA.1, BA.2 can escape Most monoclonal antibody treatments authorized by the Food and Drug Administration render them ineffective. Some treatments continue to work, such as Evusheld by AstraZeneca. The antiviral drugs Paxlovid, molnupiravir, and remdesivir remain highly effective against both variants of Omicron when taken immediately after a positive test.

When BA.2 did not show its presence in positive PCR test samples, BA.2 was designated a “hidden variant”, making it difficult for researchers to distinguish Omicron cases from Delta and other variants. BA.2 carried a mutation that hides one of the three prominent coronavirus genes that the tests detected.

Now that the vast majority of positive tests contain Omicron, the missing mutation does not matter: nearly all viruses picked up by PCR are BA.1 and those that do not are BA.2.



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