Rochelle Walensky, the director of the Centers for Disease Control and Prevention, said earlier this week that she expects the delta variant to become the dominant coronavirus strain in the United States later this year.

The delta variant, first detected in India, has already become dominant in Britain.

“As worrisome as this delta strain is with regard to its hyper transmissibility, our vaccines work,” Walensky told ABC’s “Good Morning America” on Friday. She encouraged Americans to get vaccinated and “you’ll be protected against this delta variant.”

The variant accounted for only 2.7% of all cases in May, but 9.7% of cases this month, Dr. Walensky said.

Walensky also said that next week, an advisory committee will look at reports of heart inflammation among some 300 people under age 30 who received a coronavirus vaccine.

“Over 200 million doses of vaccine have been given, and really, these events are really quite rare,” said Walensky, explaining that heart issues generally improve with rest and standard medications.

Fact check: Delta variant was not named after brain wave frequency

Both virus variants and brain wave frequencies are named using letters from the Greek alphabet. But the names have no connection.

As news about the delta COVID-19 variant made headlines, posts online began falsely claiming that the new variants were being named after brain waves or frequencies. Some posts falsely claimed this connection had to do with a secret conspiracy to control humans through technology.

For example, posts suggested that one COVID-19 variant was named delta because it largely impacts children, and they claimed that delta is a brain wave specific to children. But delta waves are actually more closely associated with deep sleep.

“Sleep is critical for development so in a contorted way you could say kids have more delta waves,” said David McCormick, professor of biology and director of the Institute of Neuroscience at the University of Oregon.

The brain has billions of neurons that are all oscillating or generating brief signals, which are also known as brain waves. The first brain wave that was discovered was the alpha rhythm, which is the rhythm prominent in the visual cortex when you close your eyes, McCormick said.

The delta COVID-19 variant was first discovered in India and is known for being more transmissible than other variants. But the variant did not get its name as part of a plot to control brains. The delta variant was named in accordance with a World Health Organization announcement from May, in which the WHO confirmed it would be changing its system for labeling COVID-19 variants.

The Greek alphabet is often used for naming purposes in math and science, not just for brain waves. Before the change, COVID-19 variants were referred to by the location where they were found along with complex alphanumeric identifiers that have to do with how a given variant has descended from those that came before.

For example, a variant found in South Africa was known as the South Africa variant, or B.1.351.

In order to get away from naming variants after their locations, which WHO said was “stigmatizing and discriminatory,” the system was changed, and the Greek alphabet was selected as the source for labeling. The variants would now be publicly known as alpha (B.1.7), beta (B.1.351), gamma (P.1) and delta (B.1.617.2).

Vaccine effort turns into slog as infectious variant spreads

Average deaths and cases per day have plummeted 90% or more across the U.S. since the winter. But the picture is uneven.

In Texas, the rolling average of newly confirmed infections has climbed from about 1,000 per day on May 31 to nearly 2,000 this week.

A swath of Missouri is seeing a big rise in cases and hospitalizations as tourists make their way to popular destinations like Branson and Lake of the Ozarks. Health officials said more than 200 people were hospitalized with the virus in southwestern Missouri, nearly double the number at the start of May. The number of patients in intensive care units in the region has tripled.

Health experts cite two factors driving the surges: the faster-spreading delta variant and a reluctance among residents to get vaccinated.

The U.S. is expected to fall short of President Joe Biden’s goal of dispensing at least one dose to 70% of American adults by July 4. The figure stands at about 65%.

Among the states that don’t expect to hit the goal are Kansas and Idaho. In Idaho, some counties have adult vaccination rates under 30%, said Elke Shaw-Tulloch, public health administrator for the state Department of Health and Welfare.

To increase vaccinations, several states are working to break up large shipments of vaccine into smaller lots, which can then be distributed to doctors’ offices. Health officials see primary care physicians as key to easing people’s concerns.

“People want to hear it from their doctor, their medical providers, people that they know and trust,” Norman said.

Big, splashy giveaways such as lotteries have also been presented as incentives, dispensing millions of dollars to vaccinated residents. In Maine, home of the outdoor-lifestyle company L.L. Bean, Bean gift cards were a big hit. But elsewhere, there has been skepticism about such programs.

Shaw-Tulloch said some businesses in Idaho had offered financial incentives for employees to get vaccinated but didn’t get many takers. Instead, she said, the key is making it easy to get a vaccine by turning it into part of a person’s “daily flow.”

Some people’s attitude is that “if a vaccine were to fall out of the sky and hit me in the arm, I’ll get it. But I’m not going to interrupt my busy daily life to make that effort and go in and get a vaccination,” she said.

She added: “That’s why we’re really focusing on walk-in clinics, pop-up clinics where, wherever they turn, there’s a place that’s easily available for getting the vaccine.”

Elsewhere around the world, there have been glimmers of hope, as India reopened the Taj Mahal amid a decline in new infections. In France, where virus cases are below 4,000 per day — down from 35,000 in the spring — authorities eased the requirements on wearing masks outdoors and said the nightly curfew will end this weekend.

“We have not known such a low level of virus spreading since last August,” Prime Minister Jean Castex said.

Meanwhile, South Africa imposed tighter restrictions on public gatherings and liquor sales as hospital admissions due to COVID-19 increased by 59% over the past two weeks, authorities said. New cases there have nearly doubled.

The recorded U.S. death toll from COVID-19 hit 600,000 on Tuesday, according to a tally by Johns Hopkins University. Worldwide, it stands at 3.8 million, though both numbers are thought to be a significant undercount.

The Associated Press contributed to this story.