Omicron is Now the Dominant Variant in the US, Accounts for 73% of All New Cases

On Monday, the US Centers for Disease Control and Prevention (CDC) estimated that the Omicron variant accounts for 73.2% of new COVID-19 cases in the United States. This report comes just 20 days after Omicron was first detected in the US.

Last week, the CDC reported that Omicron (B.1.1.529) had caused 73.2% of all new cases, with Delta accounting for 12.6%. During the previous week of December 11, Omicron accounted for just 12.6% of new COVID-19 cases, up from 1% the first week of December.

The rapid rise of Omicron overtaking other SARS-CoV-2 strains, including the infectious Alpha and Delta (B.1.617.2) variants, is testament to how the virus can become even more infectious the longer it has to mutate.

According to the World Health Organization (WHO), new Omicron infections are doubling every 1.5-3 days. In certain regions of the US, such as the Pacific Northwest, Great Lakes, Southeast, New England, and states clustered around Texas, Omicron may be responsible for over 90% of cases.

The CDC uses genomic surveillance to identify and track COVID-19 variants. Their system collects and sequences COVID-19 specimens via the National SARS-CoV-2 Strain Surveillance (NS3) program, as well as from CDC-contracted commercial or academic laboratories and state or local public health laboratories.

Though Omicron certainly seems to be more infectious, investigators are still uncertain of whether it is more severe or deadly. The first known Omicron death occurred on Monday in an unvaccinated Texas man in his 50s with underlying health conditions and a prior history of COVID-19 infection.

While Omicron has caused a massive uptick in cases in the US and across the world, infected individuals seem to have less severe disease and hospitalization than previous strains.

Available data suggests Omicron may cause more breakthrough infections, even among people who received a booster vaccine. However, health officials stressed that getting vaccinated is the best way to prevent a wave of Omicron infections from causing further strain on healthcare resources.