Dr Anthony Fauci has warned state officials against lifting coronavirus restrictions, as experts warn a new surge could impact young people.
The warning from the nation's top infectious disease expert came as Republican-led states like Texas and Mississippi have decided to ease back on coronavirus restrictions despite new variants leading to a stall in the decline in cases and hospitalisations.
"We're going in the right direction but we just need to hang on a bit longer," Dr Fauci said on CBS's Face the Nation on Sunday.
The United States experienced a decline in Covid-19 infections in the last two months following a holiday surge. But this decline has now stalled at an average of 60,000 to 70,000 new infections per day, causing concern among health officials.
More than 525,000 Americans have died from the novel virus, and January was the deadliest month since the start of the pandemic.
Dr Fauci warned that states turning restrictions "on and off" could cause another surge across the country.
"This is not going to be indefinite. We need to gradually pull back as we get people vaccinated," he said.
The warning from Dr Fauci and other experts of another surge comes from what has happened previously ahead of other surges in the virus.
"Historically, if you look back at the different surges we've had, when they come down and then start to plateau at a very high level, plateauing at a level of 60 to 70,000 new cases per day is not an acceptable level. That is really very high," Dr Fauci said.
"And if you look at what happened in Europe a few weeks ago, they're usually a couple of weeks ahead of us in these patterns, they were coming down too, then they plateaued. And over the last week or so, they've had about a 9 per cent increase in cases."
Elderly people and those with co-morbidities have been the ones most impacted by the novel virus since the start of the pandemic. But new variants have emerged as Covid-19 continues to mutate, and experts have warned younger people could be impacted more severely by newer strains.
"We're going to have some tough days ahead in the older population and in the younger population with this new variant virus," infectious disease expert Dr Michael Michael Osterholm said on NBC’s Meet the Press on Sunday.
One variant causing concern was the B.1.1.7, which was initially detected in the United Kingdom and has spread at a rapid rate through the US, now making up about 30 to 40 per cent of cases.
"And we've seen in Europe when we hit that 50 per cent mark, you'll see cases surge," Dr Osterholm said.
The country was currently working to vaccinate the vast majority of the public as new variants spread, but Dr Osterhold said that "tough days" could still be ahead in the pandemic.
"We're going to have some tough days ahead in the older population and in the younger population with this new variant virus," he said.
More than 90 million doses of the Covid-19 vaccine have been administered, and about 9 per cent of the US population has been fully vaccinated, according to data from the Centers for Disease Control and Prevention (CDC).
States have largely targeted elderly and at-risk populations to help decrease the number of people experiencing severe disease from the virus. But Dr Osterholm warned people still needed to be worried about their reaction to the virus if they become infected.
"We still have a lot of high-risk people out there," he said. "When this surge comes, they're going to be highly vulnerable."