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These 5 charts show how fast Omicron is spreading

People waited in a line spanning several blocks for COVID-19 testing on Tuesday at a testing kiosk outside an elementary school in northwest Washington.Jacquelyn Martin/Associated Press

The highly transmissible Omicron variant is driving a surge of COVID-19 cases in the United States, becoming the dominant version of the virus just weeks after it was first detected and appearing in all but a handful of US states.

The variant’s spread has prompted city and state leaders to grapple with how to respond as the holidays quickly approach and pandemic-fatigued residents get ready to spend another winter under the cloud of rapidly rising COVID-19 cases.

On Monday, Boston Mayor Michelle Wu announced new vaccine requirements for indoor dining, fitness, and entertainment venues in the city and strengthened a mandate for the city’s workers. On Tuesday, Governor Charlie Baker announced a new mask advisory that urges all residents, regardless of their vaccination status, to wear a mask in indoor, public places and said he would activate the National Guard to help hospitals. The measures came ahead of an announcement by President Biden on new initiatives to counter Omicron’s rise.

With the variant spreading, public health officials have warned that COVID-19 cases are set to rise even more. While much remains unknown about the variant, it’s clear that it’s incredibly transmissible, becoming the dominant strain in the country in just a few weeks since it was first identified.

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Here’s a look at charts that show just how quickly and widely Omicron has spread.

The variant has now been detected in all but three states in the country: Montana, South Dakota, and Oklahoma, according to the Centers for Disease Control and Prevention.

The CDC reported on Monday that Omicron is the dominant strain in the United States, making up about 73 percent of all new US cases.

That marks a dramatic shift from just one week ago, when the variant made up about 12 percent of new cases as of Dec. 11, while the Delta variant was still the most prevalent strain, accounting for 87 percent of cases.

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While Omicron is about three-quarters of cases in the US, some states are seeing an even higher proportion of the variant.

Omicron is upwards of 90 percent of cases in large swaths of the country, according to the CDC. It makes up the highest proportion of cases in northwest states like Washington, Oregon, and Idaho as well as Alaska, where 96 percent of cases in the region are Omicron.

In New York and New Jersey, Omicron cases make up 92 percent of cases, according to the CDC.

By the CDC’s estimate, the Omicron variant does not yet constitute a majority of cases in New England, however. In Maine, Massachusetts, New Hampshire, Vermont, Connecticut and Rhode Island, Omicron consists of 38 percent of the cases, while the Delta variant is still the majority of cases with 62 percent.

COVID-19 cases are surging across the country and in New England, with large stretches of the country considered to have either “high” or “substantial” transmission of the virus.

According to the CDC, roughly the entire northeastern quadrant of the United States is considered a region with high levels of community transmission. Every county in every New England state has high COVID-19 transmission rates, according to the CDC.

The Omicron variant rapidly took over as the dominant strain in the US, CDC data show.

At the beginning of the month, Omicron made up less than 1 percent of US cases, comprising just 0.7 percent by Dec. 4. By Dec. 11, that number was about 12 percent before it skyrocketed to 73 percent as of Monday.

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As the Omicron variant’s prevalence shot up, Delta’s diminished, the data show. At the beginning of the month, Delta made up 99 percent of cases, dropping slightly to 87 percent on Dec. 11 before plummeting to 26.6 percent in the CDC’s Monday report.



Daigo Fujiwara can be reached at daigo.fujiwara@globe.com. Follow him on Twitter @DaigoFuji. Amanda Kaufman can be reached at amanda.kaufman@globe.com. Follow her on Twitter @amandakauf1.