UK Coronavirus Variant Could Become Dominant US Strain By March, CDC Says

The fast-spreading variant could take off rapidly here.

The fast-spreading "U.K. variant" of the coronavirus could become the predominant strain in the United States by March, according to a new report from the Centers for Disease Control and Prevention (CDC).

About 76 cases of the new variant, known as B.1.1.7, have been detected in 10 U.S. states so far, but its ability to spread more easily than other variants means it could take off rapidly here, according to a new computer model of the spread, detailed in a report Friday (Jan. 15) in the CDC journal Morbidity and Mortality Weekly Report.

Even though this variant of SARS-CoV-2 (the coronavirus that causes COVID-19) is not thought to cause more severe illness, its projected rise is especially worrisome because more cases overall mean more hospitalizations and more deaths.

The rollout of COVID-19 vaccines will eventually reduce COVID-19 transmission significantly, but this likely won't happen until after B.1.1.7 becomes the dominant variant, according to the model.

​

In the meantime, "increased SARS-CoV-2 transmission might threaten strained health care resources, require extended and more rigorous implementation of public health strategies and increase the percentage of population immunity required for pandemic control," the authors said.

To avoid a worst-case scenario, health officials find themselves once again stressing the need to slow the spread of the virus, with masks, distancing and adherence to quarantines, which can lessen the impact of B.1.1.7 and "allow critical time to increase vaccination coverage," the authors wrote.

In the new model, the researchers assumed that B.1.1.7 currently has a prevalence of 0.5% in the U.S. among all COVID-19 infections, and that it is 50% more transmissible than other variants. The model also assumed that about 10% to 30% of the U.S. population has immunity to COVID-19 due to previous infections, and that about 1 million COVID-19 vaccine doses are administered per day beginning Jan. 1, 2021. (As of Jan. 15, about 11 million doses have been given, working out to less than 1 million doses per day, according to the CDC.)

The model projects that B.1.1.7 prevalence will grow rapidly in early 2021, and become the predominant variant in March, meaning the majority of infections will be from this variant compared with others. In the model, the rollout of vaccines didn't change the early trajectory of the variant, but kicked in later, and eventually reduced transmission significantly.

The effect of vaccines on reducing COVID-19 transmission in the near-term was greatest when transmission was already decreasing, the authors said, which further underscores the importance of slowing the virus's spread now.

This data shows "that universal use of and increased compliance with mitigation measures and vaccination are crucial to reduce the number of new cases and deaths substantially in the coming months," the authors said.

Enhanced efforts to track the evolution of SARS-CoV-2 and look for other variants of concern is also critical. The agency is currently working to bolster its surveillance in this area.

Source