By Carl O'Donnell and Jeff Mason
(Reuters) - U.S. COVID-19 cases are up around 11% over the previous week, almost entirely among people who have not been vaccinated, officials said on Thursday, as the highly infectious Delta variant becomes the dominant COVID-19 strain in the country.
Around 93% of COVID-19 cases in recent days have occurred in counties with vaccination rates of less than 40%, U.S. Centers for Disease Control and Prevention director Rochelle Walensky told a media briefing.
Preliminary data from recent months suggest 99.5% of COVID-19 deaths have occurred in unvaccinated people, she added.
"Simply put: In areas of low vaccination coverage, cases and hospitalizations are up," Walensky said.
The CDC earlier this week said that the Delta variant of COVID-19 has become the dominant strain in the United States. The variant, which is highly contagious, has also become dominant in other countries around the world.
Cases of COVID-19 are surging in counties representing 9 million people, Walensky said.
"Low vaccination rates in these counties coupled with high case rates and lax mitigation policies that do not protect those who are unvaccinated from disease will certainly and sadly lead to more unnecessary suffering," she said.
Wall Street's main indexes fell on Thursday as the spread of the COVID-19 Delta variant cast doubts over an economic recovery. [L3N2OK3CZ]
The White House is concentrating federal assistance for vaccinating against and treating COVID-19 in states including Arkansas, Missouri, Nevada and Illinois, said Jeff Zients, who leads the White House's COVID-19 response team.
The White House last week said it would send out special teams to hot spots around the United States to combat the Delta variant amid rising case counts in parts of the country.
The White House is also working to make COVID-19 vaccines available at doctors' offices around the country, Zients added.
He said the spread of the Delta variant is particularly dangerous to young people. Research suggests it may cause more severe disease among younger people than other variants of the coronavirus.
Walensky added that the United States is seeing outbreaks of COVID-19 at summer camps and other community events.
She said that both vaccinated and unvaccinated people with symptoms of COVID-19 should get tested for the virus.
(Reporting by Carl O'Donnell and Jeff Mason; additional reporting by Susan Heavey; Editing by Chizu Nomiyama, Mike Collett-White and Cynthia Osterman)