Views: 0 Author: Site Editor Publish Time: 2022-06-06 Origin: Site
Since it was first discovered in South Africa in the first two months of this year, the Omicron mutant ba 4 and ba 5. It has always been the focus of the world. This week, the latest signs showed that these two types of Omicron mutants, which still have strong escape ability in the population vaccinated with the new crown vaccine, are accelerating their transmission in the United States and are likely to replace BA in the near future 2.12.1, becoming the main epidemic strain in the United States.
According to the estimated data released by the Centers for Disease Control and Prevention (CDC) on Tuesday, in the week ending June 4, ba 5 strains accounted for about 7.6% of the total cases in the United States, ba The 4 strain accounts for about 5.4% of the total cases in the United States, and the combined proportion of the two strains has reached 13%.
Tuesday was the first time that CDC listed BA in its weekly variant report 4 and ba 5. The proportion of cases (previously, the two were classified into b.1.1529 spectrum system), which indicates that these two types of strains are beginning to attract high attention from CDC. It should be noted that in the first week of May, these two variants together accounted for only about 1% of the total number of cases in the United States.
At present, the dominant Omicron mutant in the United States is still ba 2.12.1 after climbing for several months, CDC predicts that ba 2.12.1 the strain has accounted for about 62% of the total number of new crown cases in the United States.
However, recently ba 4 and ba 5. The surge trend of the proportion of mutant cases was similar to that of BA in April 2.12.1 the trend of quietly raging in the United States is very similar, which makes more and more American people and health officials worry that these two types of mutants may be replaced in the near future.
Become the mainstream strain in the next few weeks
Nathan grubaugh, associate professor of epidemiology at Yale School of public health, predicted that "ba.4 and ba.5 may become the mainstream pedigree of Omicron in the next few weeks or months."
Grubaugh said about ba 4 and ba One of the key suspense of the 5 is whether they can beat BA in the competition 2.12.1。 According to the World Health Organization, evolving evidence shows that the early branch ba of Omicron, which triggered the surge of new crown cases last winter 1. Only ba 4 and ba 5 causes symptomatic diseases that provide limited immune protection.
For ba 4 and ba The characteristic that the mutant strain spreads more rapidly than other variants, Jesse bloom, a virus evolutionary biologist at the Seattle Research Center, said last month, "It is not clear why ba.4 and ba.5 are easier to spread, but both are closely related to ba.2. One possibility is that they are inherently better at spreading; another reason is that these variants are better at avoiding immune reactions such as antibodies, so that they can infect people with previous immunity."
Bloom's team had previously discovered ba 4 and ba It carries a key mutation called f486v in its spike protein, which is responsible for the main target of the infection immune response. This mutation can help the variant avoid the virus blocking antibody.
The US epidemic is still difficult to ease
Some health experts have warned that the spread of these new Omicron subtypes may at least prolong the time for the U.S. epidemic to extricate itself from the current wave of infection caused by other Omicron subtypes.
According to the estimation of CDC, ba 4 and ba The proportion of 5 mutants in the number of cases in Texas, New Mexico, Oklahoma, Arkansas and Louisiana is relatively high, while the proportion in the northeast of the United States is relatively low.
From the overall development trend of the COVID-19, CDC statistics show that the United States recently reported about 100000 new cases every day on average.
But many epidemiologists believe that the actual figure is much higher. The U.S. health department is basically unable to track the current wave of family self-test, which makes it more difficult to determine how many positive cases there are every day.
Some epidemiologists and doctors warn that the surge of cases will damage the social system, especially those in poor health. At the same time, many infected people may face long-term health problems. Of course, it is a little comforting that this wave of new coronal infections has not yet led to a surge in serious diseases. Although the number of hospitalizations has increased, it is still far below the earlier peak, and the newly reported death toll has recently hovered around an all-time low.
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