There has been frequent speculation that Dr Fauci's forthright approach has irked President Trump, who has been accused of downplaying the dangers of the crisis as he pushes to restart the economy.
Sanders, I-Vermont, asked Fauci about the official death toll which right now is around 80,000 in the U.S.
Democrats on the committee largely concentrated on the risks of opening the USA economy now, while Republicans downplayed that notion, saying a prolonged shutdown could have serious negative impacts on human health and the health of the economy.
Republican Senator Rand Paul attacked Dr Fauci saying "I don't think you're the end all" and also questioned the accuracy of modelling of the pandemic. "I don't know exactly what percent higher, but nearly certainly it's higher", Fauci added.
Dr. Anthony Fauci: I'm not sure Senator Sanders if it's going to be 50% higher, but most of us feel that the number of deaths are likely higher than that number.
Some of those pressuring the CDC include members of the White House coronavirus task force, including Deborah Birx, who serves as the response coordinator for the team. "We have a very large country, and the dynamics of the outbreak are different in different regions of the country, so I would imagine that situations regarding school will be very different in one region versus another".
"'Soon' isn't terribly helpful", Murphy responded.
Rand Paul Says Anthony Fauci's Not The 'End-All' In Senate Hearing
Same for the marquee witnesses - Fauci, Robert Redfield , director of the Centers for Disease Control and Prevention, and Dr. President Donald Trump has been encouraging states to end a weeks-long shuttering of major components of their economies.
"We have many candidates and hope to have multiple winners", Dr Fauci said.
As for his own humility, Fauci responded that he has "never made myself out to be the "end-all" and only voice in this".
While Fauci said it is "a reasonable assumption" that recovering coronavirus patients have developed antibodies providing some protection, only long-term studies will confirm that theory. Whoever you are, we want to hear from you so our news coverage is as complete, accurate and useful as possible. "But if we've learned anything it's that we're seeing some of these individuals who have died of the virus slip through the cracks".
"And we'd really better be very careful, particularly when it comes to children. I give advice according to the best scientific evidence", adding that it is others' jobs to give economic advice.
Some experts say testing for the virus in most parts of the country continues to fall short of what would be needed to safely reopen.
Alexander also advised for widespread screening of schools and places of work to help identify those who are sick, and therefore trace down those who are exposed.
"All roads back to work and back to school run through testing and that what our country has done so far on testing is impressive, but not almost enough", Lamar Alexander, the Republican chairman of the Senate committee, said in an opening statement to Tuesday's hearing.
Another Republican, Sen. Mitt Romney (R-Utah) called the testing in the United States "nothing to celebrate whatsoever" according to the WP article and criticized the comparison of the testing done in the United States with the testing done in South Korea as favorable. Per capita, the USA has conducted fewer tests than at least 10 other countries.