Delta Variant Went From Causing 10% to Over 50% of COVID-19 Cases: What Happens Now

• The delta variant of the coronavirus is now the dominant variant in the United States, federal officials estimate.
• The alpha variant, which once made up more than two-thirds of new COVID-19 cases in the United States, now accounts for less than one-third of cases.
• The latest CDC estimate shows the delta variant accounted for 51.7 percent of COVID-19 cases during the 2 weeks ending July 3.

The highly transmissible delta variant of the coronavirus now makes up the majority of COVID-19 cases in the United States, according to a recent estimate from the Centers for Disease Control and Prevention (CDC).

Since the delta variant was first detected in the United States in March, it quickly overtook other variants of the virus.

During the 2 weeks ending June 5, it accounted for 10.1 percent of COVID-19 cases, rising to 30.4 percent of cases by June 19.

The latest CDC estimate shows the delta variant accounted for 51.7 percent of cases during the 2 weeks ending July 3.

The alpha variant, which once made up more than two-thirds of new COVID-19 cases in the United States, now accounts for less than one-third of cases.

The rapid spread of the delta variant, also known as B.1.617.2, is not unexpected.

In the United Kingdom, which has a similar fully vaccinated rate as the United States, the delta variant quickly replaced the alpha variant. By mid-June, it accounted for around 90 percent of infections, a government study showed.

“Although we expected the delta variant to become the dominant strain in the United States, this rapid rise is troubling,” CDC Director Dr. Rochelle Walensky said in a White House COVID-19 briefing July 8.

“We know the delta variant has increased transmissibility, and it’s currently surging in pockets of the country with low vaccination rates,” she said.

In parts of the Midwest and upper Mountain States, the delta variant accounts for around 75 to 80 percent of cases, CDC data shows.

Even as the delta variant gains ground, the overall COVID-19 cases, hospitalizations, and deaths in the United States are at levels far lower than the peaks seen earlier in the pandemic.

However, “we are starting to see some new and concerning trends,” Walensky said. “Simply put, in areas of low [COVID-19] vaccination coverage, cases and hospitalizations are up.”

These increases are being seen in many states, including Nevada, Iowa, Arkansas, Alaska, and Mississippi, according to data tracked by The New York Times.

Missouri is currently a leading COVID-19 hot spot. A surge of COVID-19 cases in the southern part of the state has forced some hospitals to transfer patients to other facilities, according to local reports.

In low vaccination areas, clusters of COVID-19 outbreaks related to the delta variant have also occurred at summer camps and recreational facilities.