The new data is the first time that an overall majority of US cases have been attributed to Delta, which has been spreading quickly across the US.
The variant was first detected in the US in March. In early April it represented fewer than 0.1% of cases, meaning it surged to dominance in a space of less than three months.
The map below shows the distribution of variants by region of the US. The darkest orange is Delta, the medium shade is Gamma and the lightest orange is the Alpha variant:
According to new CDC estimates, the Delta variant made up 51.7% of cases in the US in the two weeks ending on July 3. That is up from 30.4% in the two weeks ending June 19.
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The Alpha variant, which was previously dominant in the US, caused 28.7% of cases in the same timeframe, down from 44.2% two weeks before.
A regional breakdown shows that the Delta variant is more common in Midwest and along the West Coast. It is less common in eastern states.
According to the CDC, the variant is the most common in the region made up of Iowa, Kansas, Missouri, and Nebraska, where it represents about 80% of cases.
The variant is the least common in Mid-Atlantic Region, with about 31% of Delta in Delaware, District of Columbia, Maryland, Pennsylvania, Virginia, and West Virginia.
Here's is the proportion of Delta variant per region, from most to least common:
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Region 7 (Iowa, Kansas, Missouri, and Nebraska): 80.7%.
Region 8 (Colorado, Montana, North Dakota, South Dakota, Utah, and Wyoming): 74.3%.
Region 6 (Arkansas, Louisiana, New Mexico, Oklahoma, and Texas): 58.9%.
Region 9 (Arizona, California, Hawaii, Nevada, American Samoa, Commonwealth of the Northern Mariana Islands, Federated States of Micronesia, Guam, Marshall Islands, and Republic of Palau): 57.1%.
Region 2 (New Jersey, New York, Puerto Rico, and the Virgin Islands): 56.6%.
Region 5 (Illinois, Indiana, Michigan, Minnesota, Ohio, and Wisconsin): 38%.
Region 4 (Alabama, Florida, Georgia, Kentucky, Mississippi, North Carolina, South Carolina, and Tennessee): 35.1%.
Region 1 (Connecticut, Maine, Massachusetts, New Hampshire, Rhode Island, and Vermont): 33.9%.
Region 10 (Alaska, Idaho, Oregon, and Washington): 32.4%.
Region 3 (Delaware, District of Columbia, Maryland, Pennsylvania, Virginia, and West Virginia): 31.4%.
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