CDC Director Rochelle Walensky on Wednesday said a more contagious variant of the novel coronavirus has become the most dominant strain circulating in the United States, and—in a shift in America's coronavirus epidemic—more young adults are now being hospitalized with severe cases of Covid-19.

Your top resources for Covid-19 readiness

How America's coronavirus epidemic is changing

The daily number of newly reported U.S. coronavirus cases is climbing once again, nearing the level of last summer's peak—although it's still significantly lower than the record peak reached this winter.

Good? Bad? Ugly? We've updated our take on what's next for the epidemic.

According to data compiled by the Times, the United States' average daily number of newly reported coronavirus cases over the past week was 65,556—up by 14% compared with the average from two weeks ago.

The Times' data showed that, as of Thursday morning, the rates of newly reported coronavirus cases were "staying high" in Washington, D.C and 27 states that have reported a daily average of at least 15 newly reported cases per 100,000 people over the past week. Those states are Alaska, Colorado, Connecticut, Delaware, Florida, Idaho, Illinois, Iowa, Maine, Maryland, Massachusetts, Michigan, Minnesota, Nebraska, New Hampshire, New Jersey, New York, North Dakota, Ohio, Pennsylvania, Rhode Island, South Carolina, South Dakota, Tennessee, Vermont, Virginia, and West Virginia.

In addition, the rate of newly reported coronavirus cases was "going up" as of Thursday morning in Hawaii, Indiana, Nevada, Oklahoma, Oregon, Puerto Rico, Washington, and Wisconsin, which have had comparatively lower case rates, the Times reports.

Walensky during a White House briefing on Wednesday said the B.1.1.7 variant, which was first discovered in the United Kingdom, has now become the most dominant strain circulating in the United States.

'The Never Again Plan': Moderna CEO Stéphane Bancel wants to stop the next Covid-19—before it happens

The B.1.1.7 variant's growing prevalence in the United States is further fueling concerns about a fourth surge of infections, as it is estimated to be about 60% more transmissible and 67% more deadly than the original version of the coronavirus.

Some of the states currently experiencing case spikes are largely attributing the rise to B.1.1.7. For example, health officials in Minnesota believe the B.1.1.7 variant is responsible for more than 50% of the state's recently reported cases. However, Sara Vetter, interim director of the Minnesota Health Department's Public Health Laboratory, said other factors are contributing to the spike, including people not following public health measures aimed at curbing the coronavirus's spread.

Similarly, Anthony Fauci, director of the National Institute of Allergy and Infectious Diseases and chief medical advisor for the White House's Covid-19 response, said cases are likely rising for a number of reasons, including clusters of cases in daycares and sports teams. Fauci also noted that newly reported cases appear to be skewing toward younger Americans, which he explained is likely because a majority of Americans who have been vaccinated against Covid-19 are ages 65 and older.  

Even as coronavirus cases climb throughout the country, the number of newly reported deaths linked to the coronavirus has continued to decline. According to data compiled by the Times, 2,564 new deaths were linked to the coronavirus on Wednesday, down 31% from the average two weeks ago.

Walensky said deaths have likely declined as a result of vaccinations among older Americans. According to Fauci, more than 75% of Americans ages 65 and older have received at least one dose of a Covid-19 vaccine. Overall, 110 million Americans have received at least one vaccine dose, including 64 million who have been fully vaccinated, CDC data shows.

Radio Advisory episode: How Parkland is vaccinating Dallas County—and reducing health inequity

Although vaccinations in the United States have accelerated, data shows Covid-19 hospitalizations have started to increase. According to data from the Times, 43,044 Americans with Covid-19 were hospitalized for treatment on Wednesday—up by 5% compared with the average from two weeks ago.

Walensky said hospitals are now seeing younger adults with Covid-19 hospitalized for treatment. At the beginning of the epidemic, older Americans made up a majority of Covid-19 hospitalizations, but now, Walensky said, "Hospitals are seeing more and more younger adults—those in their 30s and 40s—admitted with severe disease."

She added that, "These trends are pointing to two clear truths. One, the virus still has hold on us, infecting people and putting them in harm's way, and we need to remain vigilant. And two, we need to continue to accelerate our vaccination efforts and to take the individual responsibility to get vaccinated when we can" (Stolberg/Zimmer, New York Times, 4/7; Chow, NBC News, 4/7; Holcombe, CNN, 4/8; Ngo/Stolberg, New York Times, 4/7; New York Times, 4/8; Owens, Axios, 3/34).