A more contagious variant of the coronavirus—called B.1.1.7, which was first discovered in the United Kingdom—has now been reported in all 50 states, leading to an uptick in novel coronavirus cases and warnings from health officials against easing restrictions aimed at curbing the virus's spread.

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Coronavirus cases continue to rise 

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

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According to data compiled by the New York Times, the United States' average daily number of newly reported coronavirus cases over the past week was 64,851—up by 20% compared with the average from two weeks ago.

The Times' data showed that, as of Tuesday 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 Carolina, North Dakota, Ohio, Pennsylvania, Rhode Island, South Dakota, Tennessee, Vermont, Virginia, and West Virginia.

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

What data reveals about how variants are fueling the epidemic

CDC Director Rochelle Walensky said new cases of the novel coronavirus have been rising for four consecutive weeks in part because of the spread of variants of the virus.

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The vast majority of coronavirus patients are not tested to determine whether they have the original strain or a newer variant of the virus. However, CDC releases data on variant cases detected by limited testing. Overall, CDC data shows that the United States as of Tuesday reported 16,174 total cases of certain novel coronavirus variants across 50 U.S. states and territories, including:

• 15,511 cases of the B.1.1.7 variant, which research suggests is more transmissible and may be less susceptible to current Covid-19 vaccines than earlier variants of the novel coronavirus, as well as potentially more deadly than earlier variants of the virus;
  
  
• 374 cases of the B.1.351 variant first identified in South Africa, which research suggests is more transmissible and may be less susceptible to current Covid-19 vaccines than earlier variants of the virus; and
  
  
• 289 cases of the P.1 variant first identified in Brazil, which research suggests is more transmissible and may be less susceptible to current Covid-19 vaccines than earlier variants of the virus.

Sebastian Funk, a professor of infectious disease dynamics at the London School of Hygiene and Tropical Medicine, said, "The best way to think about B.1.1.7 and other variants is to treat them as separate epidemics," because "[w]e're really kind of obscuring" their role in the epidemic "by adding them all up to give an overall number of cases."

For example, as of March 13, the B.1.1.7 variant was estimated to account for about 27% of the United States' new coronavirus cases—up from 1% of cases in February, the Times reports.

Experts now say the United States is caught in a race between variants and vaccines. According to the Times, 31% of Americans have received at least one vaccine dose, and only 17% of Americans have been fully vaccinated against Covid-19.

Michael Osterholm, director of the University of Minnesota's Center for Infectious Disease Research and Policy, said Covid-19 vaccines are very effective against the new variants of the coronavirus, but the United States may not be able to administer enough vaccine doses to avoid another surge in cases. 

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"We are not going to have enough vaccines, the way we are going, into the arms of enough Americans over the course of the next six to ten weeks with this surge that we are going to stop it," Osterholm told CNN's Erin Burnett. "It's just simply not going to happen."

However, other experts are more optimistic. Paul Offit, a vaccine expert at Children's Hospital of Philadelphia and a member of FDA's Vaccines Advisory Committee, said he believes a few factors could help the United States prevent another spike in coronavirus cases this spring, including the warmer weather, the increase in vaccination rates, and the significant share of Americans who have already been infected with the coronavirus.

Fauci urges Americans to continue to follow measures aimed at curbing coronavirus's spread

Anthony Fauci, director of the National Institute of Allergy and Infectious Diseases and chief medical advisor for the White House's Covid-19 response, during a White House coronavirus briefing said Americans should continue to follow public health measures intended to curb the coronavirus's spread as summer approaches and temperatures rise.

"You might remember a little bit more than a year ago when we were looking for the summer to rescue us from surges. It was, in fact, the opposite," Fauci said. "We saw some substantial surges in the summer. I don't think we should even think about relying on the weather to bail us out of anything we're in right now."

Similarly, Ashish Jha, dean of Brown University's School of Public Health, told CNN's Wolf Blitzer that it's crucial for Americans to continue to take precautions to protect themselves and others from the coronavirus.

"We're not there yet and the variants make it particularly concerning," Jha said. "We really do have to hunker down for a few more weeks. We are very close to the finish line but we can't stop yet" (New York Times, 4/5; Holcombe, CNN, 4/6; Genomeweb/Modern Healthcare, 4/4; Mandavilli/Mueller, New York Times, 4/3; Macias, CNBC, 4/5).