WASHINGTON (CN) — While President Donald Trump continues to mislead the public about the spread of the coronavirus, career health officials testified before Congress on Tuesday with facts and a clear message to the American people: do not panic.

“When you are in the area of the unknown, you have to walk a delicate balance of not overshooting and having panic,” said Dr. Anthony Fauci, director of the National Institute of Allergy and Infectious Diseases, “but not also undershooting and be in a situation where you don’t respond as aggressively as you should.”

Fauci, a top federal disease expert across decades of presidential administrations, testified to the known facts on the spread of the novel coronavirus, known as Covid-19, debunking many of Trump’s false claims over the last week.

With rumors on the rise about what Americans can do to steer clear of coronavirus, health officials testified to the Senate Committee on Health, Education, Labor and Pension that the disease will continue to spread to cities across the U.S. The virus has hit 65 countries around the world, with the total number of cases topping 90,000 and fatalities up to 3,000.

Eclipsing Trump’s initial $1.5 billion proposal, Congress as of Tuesday is reportedly wrapping up a $7.5 billion package to battle the virus.

While the spread of respiratory diseases like the seasonal flu slows as the weather warms, Fauci testified that there is no evidence that coronavirus cases will decrease over the next month, as Trump has repeatedly claimed.

The director said he recalled during Tuesday’s hearing that more than 30 years ago he testified in the same room explaining that HIV was not created by the CIA to eliminate homosexuals and African-Americans.

“It’s crazy,” Fauci said. “But this is what happens when you have outbreaks. There is a lot of misinformation.”

Dr. Anne Schuchat, principal deputy director at the Centers for Disease Control and Prevention, said that “the situation is evolving and dynamic,” with more than 1,500 CDC officials responding to the outbreak.

“We don’t want to have the health care system flooded with people who don’t need to be there,” Schuchat said. “But if this is going to be like a really bad flu, we are going to need to build up that health care system.”

Experts assured the senators that 80% of coronavirus cases will be mild, with symptoms including a fever and chest cough — and not the sore throat, sneezing and sinus pressure common with the seasonal flu — while 20%, primarily elderly patients, will require hospitalization.

Six U.S. patients have died from coronavirus, all in Senator Patty Murray’s home state of Washington.

The Democrat called the Trump administration’s response to the outbreak unacceptable, and stressed that low income workers have been told to stay home if they are sick due to a shortage of test kits, many without guaranteed paid leave.

“To put it simply, if someone at the White House or in this administration is actually in charge of responding to the coronavirus virus it would be news to anybody in my state,” Murray said.

Dr. Stephen Hahn, commissioner of the Food and Drug Administration, said the FDA and CDC are working to rapidly increase the number of test kits in health labs in all 50 states to 2,500 by the end of the week.

“Our expectation, in talking to the company that is scaling this up, is that we should have the capacity by the end of the week to have kits available to the laboratories to perform about a million tests,” Hahn said, later adding that each kit can carry out 500 tests.

Several expert witnesses assured the committee that federal officials are working closely with private manufacturers to develop a vaccine. But Fauci, among them, said while experts are working with record speed, a vaccine will require several testing phases over the next year.

“We hope that we will be able to get good news to you…but there will be no guarantee of that,” Fauci said, contradicting Trump’s claim that a vaccine may be available “relatively soon.”

As for a drug to combat coronavirus, labs are rushing to develop a new treatment. Hahn was unable to confirm as of Tuesday’s hearing whether India restricting the export of 26 active pharmaceutical ingredients as part of the country’s response to the outbreak would slow that push.

Senator Murray honed in on reports that CDC first responders who boarded the Diamond Princess cruise ship, during a widespread outbreak of coronavirus on board, were not appropriately trained and failed to wear protective gear.

Dr. Robert Kadlec, assistant secretary for preparedness and response at the Department of Health and Human Services, said his agency is “evaluating what may have been a breach” after a whistleblower raised the alarm about the Diamond Princess response.

“We need people to speak up when they see these situations,” Murray said. “It is unacceptable if any of these workers on the front lines are intimidated into staying silent or believe that they are going to be retaliated against.”

Asked by Murray if they would commit to providing the full truth about coronavirus to the public — even if that means contradicting a tweet by Trump — all four health officials testifying Tuesday responded to the top Democrat on the committee with a resounding yes.