Explainer: Omicron’s “Stealth” COVID variant BA.2 has gained worldwide dominance

Police officers and officials said on March 24, 2022, in Shanghai, China, a temporary nucleic acid testing center within a barrier in a closed area in the midst of a coronavirus disease (COVID-19) outbreak. I will be tested for coronavirus disease (COVID-19). / Allie Song

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March 29 (Reuters)-A highly infectious version of the coronavirus subvariant known as BA.2 is now predominant worldwide, surged in many countries in Europe and Asia, and in the United States. There is growing concern about the potential for new waves. state.

The following is a summary of what is known about BA.2.

More contagious

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According to the World Health Organization, BA.2 currently accounts for nearly 86% of all sequenced cases. This is even more contagious than the highly contagious siblings of Omicron, BA.1 and BA.1.1, but the evidence so far is more likely to cause severe illness.

Like other variants of the Omicron family, the vaccine is less effective against BA.2 than previous variants such as Alpha and the original coronavirus strain, and protection declines over time. However, protection has been restored, according to data from the UK Health and Security Agency. Especially by booster jabs to prevent hospitalization and death. https: // /

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The rise in BA.2 is due to the recent surge in China and record infections in European countries such as Germany and the United Kingdom.

BA.2 is called a “stealth variant” because it is a bit difficult to track. Since BA.1 lacks the gene, it can be tracked by default in regular PCR tests. BA.3, another sibling of BA.2, has also increased prevalence, but is currently at low levels, but can only be found by genomic sequencing. This is doing more in some countries than in others.


An important concern about BA.2 was whether it could re-infect people who already had BA.1. Especially because in many countries the “double peaks” of infection rates seemed surprisingly close. However, both UK and UK data Denmark can reinfect people who had other variants such as Delta, while only a handful of people who had BA.1 BA. .2 Reinfection has been shown to have been found in tens of thousands of cases so far.

Scientists say the possible explanation for the recent rise in BA.2 may be that a global rise occurred at the same time that many countries lifted public health intervention.

Dr. Andrew Pekosi, a virologist at the Johns Hopkins Bloomberg School of Public Health in Baltimore, said:

As a result, other US experts, such as Eric Topol, director of the Scripps Research Translational Institute in La Jolla, California, said it was “a little too early” to decide whether the US would see an important BA.2 wave as well. “.

But whatever the reason for the rise in BA.2, scientists said they reminded us that the virus continues to do harm, especially among unvaccinated, unvaccinated and vulnerable populations. ..

“This is still a major public health problem and will continue,” said Mark Woolhouse, an epidemiologist at the University of Edinburgh.

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Report by Jennifer Rigby and Julie Steen Heisen, edited by Michele Garschberg

Our Criteria: Thomson Reuters Trust Principles.


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