British coronavirus strain doubles in US every 10 days, study finds

The strain of mutant coronavirus first identified in the UK remains at low levels in the US but doubles its range about every 10 days, according to a study released by researchers on Sunday.

The study bolstered modeling done by the Centers for Disease Control and Prevention, which predicted last month that the most contagious variant could be the dominant strain in the United States by March.

The United States still has time to take action to slow down the new viral strain, the researchers wrote, but warned that without “decisive and immediate public health action”, the variant “would likely have devastating consequences for the virus. mortality and morbidity from COVID-19 in the United States within a few months. “

The research, funded in part by the CDC and the National Institutes of Health as well as the Canadian Institutes of Health Research, has been posted to medRxiv, a pre-print server, and has not yet been reviewed. peer review.

The new strain of coronavirus, also known as B.1.1.7, has spread rapidly across the UK and has become the dominant strain in this country, which is by some measures the hardest hit in Europe .

Health officials have said existing vaccines are likely to work against new strains, although their effectiveness may be somewhat reduced.

The study revealed that there are “relatively small” amounts of B.1.1.7. in the United States at the moment but that, given its rapid spread, it is “almost certainly destined to become the dominant strain of SARS-CoV-2 by March 2021”.

The new strain accounted for 3.6% of coronavirus cases in the United States during the last week of January, according to the study.

The researchers noted that tracking the national spread of the strain is complicated by the lack of a national genomics monitoring program like those found in the UK, Denmark and other countries.

They wrote that they had “relatively robust” estimates from California and Florida, but data outside of those states was limited.

The growth rate of the virus diverged in the two states, with B.1.1.7. appearing to be spreading a bit slower in California. The study authors wrote that the strain doubled about every 12.2 days in California, 9.1 days in Florida, and 9.8 days nationwide.

The study supports the conclusion that the new strain is already spreading via “significant community transmission”.

The authors suggest the virus was brought into the country via international travel and spread via domestic travel as millions of Americans crossed the country during the Thanksgiving, Christmas and New Years holidays during the fall and winter.

The authors also found that the variant developed a bit slower than in European countries, a fact that they believe needs further investigation, but may be the result of current data scarcity or other factors – including “competition from other more transferable variants”.

Other worrying coronavirus strains have been detected in South Africa and elsewhere.

The researchers have warned that their findings “reinforce the need” for robust surveillance in the United States of possible new and emerging coronavirus variants.

“Because laboratories in the United States are only sequencing a small subset of SARS-CoV-2 samples, the true diversity of SARS-CoV-2 sequences in this country is still unknown,” they said. written.

“More established surveillance programs in other countries have provided important warnings about variants of concern that may impact the United States, with B.1.1.7 representing only one variant that demonstrates the capacity for growth exponential, ”they added.

“Only with consistent and impartial sequencing at a scale that includes all geographic and demographic populations, including those often under-represented, along with continued international scientific collaborations and open data sharing, will we be able to to accurately assess and track new variants that emerge during the COVID-19 pandemic, ”the researchers wrote.