More Transmissible Variant Could Dominate by March, CDC Warns

Damian McNamara

January 15, 2021

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Just over 1 month since UK investigators cautioned the world about the emergence of a new, more transmissible SARS-CoV-2 variant, Centers for Disease Control and Prevention (CDC) investigators warn this new one will predominate across the United States by March.

As of January 13, the B.1.1.7 variant of SARS-CoV-2 was detected in 76 cases across 10 US states, researchers report January 15 in an early release of the CDC's Morbidity and Mortality Weekly Report (MMWR). 

Their modeling predicts rapid growth of B.1.1.7 in early 2021.

The potential implications are many. A threat to already strained healthcare resources and a need for expanded and more rigorous public health strategies are likely, for example.

Furthermore, "increased transmissibility also means that higher-than-anticipated vaccination coverage must be attained to achieve the same level of disease control to protect the public compared with less-transmissible variants," note lead study author Summer E. Galloway, PhD, and colleagues with the CDC COVID-19 Response Team, and Office of Advanced Molecular Detection.

No Time to Waste

The report comes as new US COVID-19 case numbers continue to rise and break records. The CDC researchers reemphasize tactics to control the pandemic, particularly in light of the B.1.1.7 variant, including the well-known mask-wearing, distancing, hand hygiene, isolation, and quarantine measures. 

These public health strategies are essential to lessen the potential impact of B.1.1.7, "buying critical time to increase vaccination coverage," Galloway and colleagues note.

However, they also add a need to enhance genomic surveillance of SARS-CoV-2 variants.

The prediction modeling also considers the effects of COVID-19 vaccination. The researchers estimated 1 million vaccine doses daily beginning January 1, 2021, and 95% effectiveness at 14 days after the second immunization. They also assumed equal protection afforded by the vaccines for the existing virus and the new variant.

"With vaccination that protects against infection, the early epidemic trajectories do not change and B.1.1.7 spread still occurs. However, after B.1.1.7 becomes the dominant variant, its transmission [is] substantially reduced," the researchers note.

The heightened transmissibility of B.1.1.7 stems from multiple genetic mutations along the virus' spike protein, including one that changes the shape of its receptor-binding domain.

Monitoring a Variety of Variants

B.1.1.7 is not the only variant causing global concern. A variant detected in South Africa and another identified in Tokyo in four travelers from Brazil are likewise believed to feature enhanced transmissibility. But as of January 12, neither of these strains has been detected in the United States.

"Evidence suggests that other mutations found in these variants might confer not only increased transmissibility but might also affect the performance of some diagnostic real-time reverse transcription polymerase chain reaction (RT-PCR) assays and reduce susceptibility to neutralizing antibodies," the researchers note.

The newly established CDC National SARS-CoV-2 Strain Surveillance (NS3) program will continue to monitor SARS-CoV-2 variants. Visit the CDC's Emerging SARS-CoV-2 Variants web page for updated information.

MMWR. Published online January 15, 2021. Full text

Damian McNamara is a staff journalist based in Miami. He covers a wide range of medical specialties, including infectious diseases, gastroenterology, and critical care. Follow Damian on Twitter: @MedReporter.

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