Without proper preparations, Fauci said he feared that “we will start to see little spikes that might turn into outbreaks,” and that “the consequences could be really serious”.

His comments throughout the hearing reiterated points he made in the email he sent to The New York Times on Monday in which he wrote: “If we skip over the checkpoints in the guidelines to: ‘Open America Again,’ then we risk the danger of multiple outbreaks throughout the country. This will not only result in needless suffering and death, but would actually set us back on our quest to return to normal.”

Fauci gave his testimony from home – where he is under self-quarantine – to a mostly empty meeting room. Many senators present wore masks, while others conferenced in from their homes.

Fauci, the director of the National Institute of Allergy and Infectious Diseases and a key member of the White House coronavirus task force, was joined by the three senior health officials: Food and Drug Administration commissioner Dr Stephen Hahn, Centres for Disease Control and Prevention director Dr Robert Redfield and the Assistant Secretary for Health Admiral Brett Giroir.

Coronavirus: Dr Fauci quarantining along with two other task force members

In his opening remarks, Redfield – also at home in self-quarantine – called upon the nation to seize this opportunity to strengthen the nation’s health care system.

“We need to rebuild our nation’s public health infrastructure,” he said. “Now’s the time to put it in place for the generations to come, not only for the public health system that our nation needs, but for the public health system our nation deserves.”

Fauci used his testimony to caution states against moving too quickly, repeatedly called upon leaders to rely on hard data and to follow guidelines on reopening put out by the federal government. His words came as many states moved forward with reopening even as only 33 states have met even the most basic benchmark for reopening – a 14-day downward trajectory in new cases and infection rates – according to an Associated Press analysis.

When asked if the virus would effectively go away on its own, a scenario occasionally put forth by the White House, Fauci demurred. “That is just not going to happen,” he said.

And Fauci did not share the level of optimism of Trump, who said on Monday afternoon that “we have met the moment and we have prevailed”.

Under questioning by Democratic Massachusetts Senator Elizabeth Warren, Fauci struck a different tone.

“If you think we have it completely under control, we don’t,” he said. “I think we are going in the right direction, but the right direction does not mean we have, by any means, total control of this outbreak.”

Still, anyone hoping for a partisan sound bite was disappointed.

When pressed by Republican Utah Senator Mitt Romney – who has emerged as a rare critic of the Trump administration within the Republican Party – whether it would be fair to say that either former president Barack Obama or Trump were responsible for the United States not having a vaccine, the doctor did not mince words: “Certainly, neither President Obama nor President Trump are responsible for not having a vaccine.”

Fauci dismisses coronavirus lab origin claims as ‘circular argument’

And Fauci tempered his serious warnings with good news, including his confidence the country would ramp up testing to where it was needed and that a vaccine will be developed. Fauci touted the speed of the nation’s response especially in terms of vaccines, saying that multiple vaccines were in development and testing at the same time, and that we should have a good idea of whether they work by late fall or early winter.

Asked by Romney whether an effective vaccine within a year or two was a “long shot”, Fauci said: “Definitely not.”

“It is more likely than not, that we will, because … the overwhelming majority of people recover from this virus,” he explained. “The very fact that the body is capable of spontaneously clearing the virus tells me that at least from a conceptual standpoint, we can stimulate the body with a vaccine that would induce a similar response.”

Tuesday’s testimony is likely the only time that Fauci will face questions from Democratic lawmakers.

President Trump has mostly blocked members of the coronavirus task force from testifying to Congress, especially the Democrat-controlled House, calling the House a “set-up” and “a bunch of Trump haters.”

Additional reporting by Robert Delaney