Dr. Fauci to Issue stark Warning on Risks of Reopening soon.

Dr. Anthony S. Fauci, the nation’s top infectious disease expert and a central figure in the government. He response to the coronavirus, intends to warn the Senate on Tuesday that Americans would experience “needless suffering and death” if the country opens up too quickly.

Dr. Fauci, who has emerged as perhaps the nation’s most respected voice during the coronavirus crisis, is one of four top government doctors scheduled to testify remotely at a high-profile hearing on Tuesday before the Senate Health Education, Labor and Pensions Committee.

It will be his first appearance before Congress since President Trump declared a national emergency in March, and a chance for him to address lawmakers and the public without President Trump by his side. He has been largely out of public view since last week, when Mr. Trump abandoned his daily briefings with his coronavirus task force.

In an email to the New York Times reporter Sheryl Gay Stolberg late Monday night, Dr. Fauci laid out what he intended to tell senators.

“The major message that I wish to convey to the Senate HLP committee tomorrow is the danger of trying to open the country prematurely,” 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.”

Dr. Fauci was referring to a three-phase White House plan, Opening Up America Again, that lays out guidelines for state officials considering reopening their economies. Among its recommendations: States should have a “downward trajectory of positive tests” or a “downward trajectory of documented cases” of coronavirus over two weeks, while conducting robust contact tracing and “sentinel surveillance” testing of asymptomatic people in vulnerable populations, such as nursing homes.

But many states are reopening without meeting those guidelines, seeking to ease the economic pain as millions of working people and small-business owners are facing ruin while sheltering at home.

“We’re not reopening based on science,” said Dr. Thomas R. Frieden, a former director of the Centers for Disease Control and Prevention. “We’re reopening based on politics, ideology and public pressure. And I think it’s going to end badly.”

The much-feared second wave of infection may not wait until fall, many scientists say. Instead, it may become a series of wavelets occurring unpredictably across the country.

Dr. Fauci himself is now in “modified quarantine,” he has said, after what he described as a “low risk” exposure to someone infected with the virus.