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The variant now makes up 10% of all new cases in the United States, up from 6% last week. Studies have shown the variant is even more transmissible than other variants. WHO officials said some reports have found that it also causes more severe symptoms, but more research is needed to confirm those conclusions.
The WHO is also tracking recent reports of a “delta plus” variant. “What I think this means is that there is an additional mutation that has been identified,” said Maria Van Kerkhove, the WHO’s Covid-19 technical lead. “In some of the delta variants we’ve seen one less mutation or one deletion instead of an additional, so we’re looking at all of it.”
The United Kingdom recently saw the delta variant become the dominant strain there, surpassing its native alpha variant, which was first detected in the country last fall. The delta variant now makes up more than 60% of new cases in the U.K.
Dr. Anthony Fauci, chief medical advisor to the president, said last week that “we cannot let that happen in the United States,” as he pushed to get more people vaccinated, especially young adults.
The Centers for Disease Control and Prevention designated the delta variant as a variant of concern in the U.S. on Tuesday. The WHO designated the delta variant as a variant of concern in early May.
The WHO on Tuesday also added another Covid mutation, the lambda variant, to its list of variants of interest. The agency is monitoring more than 50 different Covid variants, but not all become enough of a public health threat to make the WHO’s formal watchlist. The lambda variant has multiple mutations in the spike protein that could have an impact on its transmissibility, but more studies are needed to fully understand the mutations, Van Kerkhove said.
The lambda variant has been detected by scientists in South America, including in Chile, Peru, Ecuador and Argentina, thanks to increased genomic surveillance.