New Covid-19 variant linked to higher viral load in the blood

Scientists say B117 56% more transmissable than previous variant, US reports covid variant

The hypothesis that the fast-spreading UK variant of the Covid-19 virus has a transmission advantage has been bolstered by an analysis that suggests it is linked to higher loads of the virus in the blood.

The variant, named B117, was discovered during an investigation into why coronavirus cases in Kent continued to rise during the November lockdown. Scientists found it continued to spread during the restrictions while older variants declined.

Some of the lighthouse laboratories created in April to boost Covid-19 testing capacity in places such as London and Manchester were beginning to see evidence of the new variant in samples when the Covid-19 Genomics UK consortium sounded the alarm about B117 and its transmission advantage.

Dr Michael Kidd, of the PHE Public Health Laboratory in Birmingham, and his team analysed a total of 641 samples based on tests from symptomatic patients and found evidence of B117 among other variants. About 35 per cent of patients infected by B117 had high levels of the virus in their samples, compared with 10 per cent of patients without the variant, they said in their still-to-be-peer reviewed study.

“It does seem as though the patients with this variant have higher viral loads - then the obvious thing is it is easier for them to spread it to other people,” Mr Kidd said, cautioning that the data was preliminary and more evidence needed to be collected before firm conclusions could be drawn.


Scientists say they have high confidence that B117 has a transmission advantage – a modelling study by London School of Hygiene and Tropical medicine researchers has estimated it is about 56 per cent more transmissible than previous variants.

A plethora of factors could explain why it is more transmissible. If the variant is more infectious, then fewer virus particles are needed in the host to pass the pathogen on. The virus might also replicate faster in the airways, or make people infectious for longer, making them more likely to transmit the virus.

“Exactly how it [ the variant] reaches a high viral load is another big question,” said Kidd, adding that laboratory-based confirmation is required to understand the biological basis of the transmission advantage.

“Like pieces in a jigsaw we need other evidence and I think the importance of this study is - although it’s preliminary and needs repeating - it does offer a sort of on the ground explanation of why this virus may have the ability to spread more easily – because patients are more infectious.”

Early data suggests the UK variant does not make people sicker or increase the likelihood of reinfection or death. But a higher rate of transmissibility without strict controls could still lead to more death.


A man in Colorado has become the first known US case of the newly identified strain of Covid-19 circulating in the UK. The new variant is thought to be more contagious than other, established variants and has prompted some countries to restrict travel from the UK.

The Colorado man who contracted the new variant, called B117, is in his 20s, and had no travel history, according to the state’s health department. In a statement, Governor Jared Polis said that health officials are conducting an investigation into how the man might have contracted the virus, while he recovers in isolation.

Although the new variant had not been found in the US until now, the Centres for Disease Control and Prevention noted that it was likely already circulating through the country. The agency said while the new variant has not been identified through sequencing efforts “labs have only 51,000 of the 17 million US cases” - and the variant might not have been picked up.

"Ongoing travel between the United Kingdom and the United States, as well as the high prevalence of this variant among current UK infections, increase the likelihood of importation," the CDC said in a statement. "Given the small fraction of US infections that have been sequenced, the variant could already be in the United States without having been detected."

The new variant has also recently been detected in at least 17 countries, including South Korea, Spain, Australia and Canada. On Christmas Day, the CDC issued new guidelines for travellers from the UK, requiring proof of a negative Covid-19 test.

Travel history

That the Colorado man who tested positive for the new variant has no travel history is significant in that it suggests the new variant is already spreading through US communities, said Carlos del Rio, an infectious disease expert at Emory University, in a tweet.

“There is a lot we don’t know about this new Covid-19 variant, but scientists in the United Kingdom are warning the world that it is significantly more contagious,” Polis said in a statement. “We are working to prevent spread and contain the virus at all levels.”

New variants of the coronavirus have been seen almost since the virus was first detected in China nearly a year ago. It is common for viruses to undergo minor changes as they reproduce and move through a population.

The US, unlike the UK, has not broadly and consistently been tracking genomic sequences of Covid-19 infections and has a less robust process for tracking viral mutations.

“The fact that Colorado has detected this variant first in the nation is a testament to the sophistication of Colorado’s response,” said Jill Hunsaker Ryan, the executive director of the state’s public health department, in a statement. “We are currently using all the tools available to protect public health and mitigate the spread of this variant.”

The US has recorded more than 19.46 million cases of the coronavirus, more than any other country. Even as health workers, elderly people and other Americans start receiving their first doses of coronavirus vaccines developed by Moderna and Pfizer, the country has found itself battling a massive surge of cases. In some parts of the country, including Los Angeles, hospitals have found themselves overwhelmed, forced to turn away ambulances. – Guardian