Study estimates 67% of cases between December and February were linked to UK variant

About two-thirds of all U.S. coronavirus cases identified over the past three months may be linked to the variant first identified in the UK, a new study suggests.

There are at least 11,569 cases of the strain, known as B 1.1.7, in the U.S., according to the Centers for Disease Control and Prevention (CDC). 

But researchers believe the true number could be much higher and found that between December 2020 and February 2021, 67 percent of samples came back positive for the mutation.

Because of its more contagious nature, infections of the variant in the U.S. appear to be doubling about every nine days and spreading 40 to 50 percent faster than previous variants. 

The team, led by the Scripps Research Institute, says the findings provide evidence that B.1.1.7 may now be the country’s dominant variant.

There are at least 11,569 cases of the strain, known as B 1.1.7, in the U.S., with cases confirmed in almost every U.S. state

There are at least 11,569 cases of the strain, known as B 1.1.7, in the U.S., with cases confirmed in almost every U.S. state

There are at least 11,569 cases of the strain, known as B 1.1.7, in the U.S., with cases confirmed in every U.S. state

But a new study found that, between December 2020 and February 2021, 67% of samples genetically sequenced came back positive for the variant

But a new study found that, between December 2020 and February 2021, 67% of samples genetically sequenced came back positive for the variant

But a new study found that, between December 2020 and February 2021, 67% of samples genetically sequenced came back positive for the variant

Because of its more contagious nature, infections of the variant in the U.S. appear to be doubling about every nine days and spreading 40 to 50% faster than previous variants

Because of its more contagious nature, infections of the variant in the U.S. appear to be doubling about every nine days and spreading 40 to 50% faster than previous variants

Because of its more contagious nature, infections of the variant in the U.S. appear to be doubling about every nine days and spreading 40 to 50% faster than previous variants

‘B.1.1.7 rapidly became the dominant SARS-CoV-2 variant in the U.K. and other countries after its emergence late last year, and the U.S. is now on a similar trajectory,’ says study co-senior author Dr Kristian Andersen, a professor in the Department of Immunology and Microbiology at Scripps Research.

‘We need immediate and decisive action to minimize COVID-19 morbidity and mortality.’ 

The UK variant was first discovered in the county of Kent in September but was not deemed a ‘Variant of Concern’ (VOC) until December.

Its name, B.1.1.7, derives from the location of its most significant mutations.

It now accounts for at least 90 percent of all cases in Britain.

Most estimates put it at about 70 percent more infectious than older ‘wild-type’ coronavirus variants, but more moderate projections say its transmissibility is only about 56 percent higher. 

This is because one of the variant’s many mutations is to the spike protein, which the virus uses to enter and infect human cells.   

Standard tests for coronavirus look for distinctive genetic sequences at three sites but, because of B.1.1.7 variant’s mutations, only two come back positive.

For the first part of the analysis, published in the journal Cell,, the team looked for this pattern, called the S-gene target failure, among 500,000 samples of the virus, tested at Helix facilities since July 2020.  

Beginning the week of October 18 just 0.2 percent of daily positive cases appeared to be linked to the UK variant.

This slowly increased to 0.8 percent in the first week of January to 10.6 percent in the third week of February. 

In the second part of the analysis, the researchers performed genome sequencing on all SGTF samples from December 2020 through February 2021

Cases involving the new variant are most prevalent in Florida (top graph) and California (bottom graph), doubling every 8.7 days and 6.9 days, respectively

Cases involving the new variant are most prevalent in Florida (top graph) and California (bottom graph), doubling every 8.7 days and 6.9 days, respectively

Cases involving the new variant are most prevalent in Florida (top graph) and California (bottom graph), doubling every 8.7 days and 6.9 days, respectively

CDC director Dr Rochelle Walensky revealed on Wednesday that B.1.1.7 makes up between 4% to 35% of coronavirus cases depending on the region

CDC director Dr Rochelle Walensky revealed on Wednesday that B.1.1.7 makes up between 4% to 35% of coronavirus cases depending on the region

CDC director Dr Rochelle Walensky revealed on Wednesday that B.1.1.7 makes up between 4% to 35% of coronavirus cases depending on the region

Of the 986 samples, 662 of them – or 67 percent – contained the B.1.1.7 variant. 

Researchers found the majority of B.1.1.7 sequences from the U.S. cluster were in three states: Florida, California and Georgia.

The new report estimates that cases are doubling in California every 6.9 days, in Florida every 8.7 days and every 9.2 day in Georgia. 

Michigan officials say the recent spike in cases seen in the state is likely due to the variant. 

‘B.1.1.7 has a doubling rate of a little over a week and an increased transmission rate of 40-50 percent, which means it could have a meaningful impact on public health,’ says Lee. 

‘It is critical that we continue to monitor the spread of this and other emerging variants, but our current level of surveillance is inadequate and lags behind that of other countries. We need a more comprehensive national SARS-CoV-2 genomics surveillance program to address this.’

During a press conference on Wednesday, CDC director Dr Rochelle Walensky revealed that B.1.1.7 makes up between four percent to 35 percent of coronavirus cases depending on the region.

She says the CDC believes the variant currently makes up 26 percent of cases across the nation.

‘We’re watching this very carefully but it is starting to become the predominant variant in many U.S. regions,’ Walensky said.

‘We’re starting to see it creep up. We do know it’s more transmissible, somewhere between 50 percent and 70 percent more transmissible than the wild type strain, so to the extent people are not practicing the standard mitigation strategies, we do think that more infections will result because of B.1.1.7.’ 

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