UK coronavirus variant likely circulated undetected in US for months, researchers say

The more transmissible coronavirus variant first detected in the U.K. likely made its way to the U.S. months before it was discovered, according to a new analysis by researchers. In fact, the B.1.1.7 variant was likely “silently spreading” in 15 other countries before being identified in the U.K. in December 2020.

“By the time we learned about the U.K. variant in December, it was already silently spreading across the globe,” Lauren Ancel Meyers, director of the COVID-19 Modeling Consortium at The University of Texas at Austin, and professor of integrative biology, said in a news release posted to Eurekalert.org. “We estimate that the B.1.1.7 variant probably arrived in the U.S. by October of 2020, two months before we knew it existed.”

The University of Texas at Austin COVID-19 Modeling Consortium team, which published an early-release version of its findings in the journal Emerging Infectious Diseases, analyzed data from 15 countries and estimated the chance that travelers from the U.K. spread the variant to those regions between Sept. 22 and Dec, 7, 2020. The September date was chosen as, according to the data, the B.1.1.7 variant was detected in samples initially collected in Kent on September 20 and London on September 21.

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They based the estimation on the “changing proportion of infections” driven by the variant in the U.K. and population mobility from the U.K. to each of the 15 countries, which they pulled from Facebook Data for Good.

“By October 22 (a month after the variant was first detected in the United Kington), the chance that 01 of the 15 countries would receive 1 imported case from the United Kington was at least 50%, except for Romania, Portugal, Cyprus, India and the United States, although by November 1, this risk threshold was exceeded for all of these countries,” the researchers wrote.

The team based their projections on travel from the U.K.
(iStock)

Using these projections, the team concluded that countries with substantial population movement from the U.K. were likely to have undetected cases of the variant by late October 2020.

“This study highlights the importance of laboratory surveillance,” Meyers said, in the news release posted on Eurekalert.org. “Rapid and extensive sequencing of virus samples is critical for early detection and tracking of new variants of concern.”

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The team also released a new online calculator meant to determine the number of virus samples that need to be sequenced in order to detect new variants when they first emerge.