Dr. Anthony Fauci, the director of the National Institute of Allergy and Infectious Diseases, spoke to Trevor Noah on a social distancing episode of the "The Daily Show" on Thursday.

While he didn't mention Trump directly, he did criticize his intention to open the country in two weeks.

He said that a date to reopen the country can't be chosen "arbitrarily" because the "virus is the clock."

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Dr. Anthony Fauci, the director of the National Institute of Allergy and Infectious Diseases, seemingly criticized President Donald Trump's intent to relax restrictions on the United States economy by Easter, saying the nation can't "arbitrarily" pick a date that things will go back to normal.

Fauci spoke to Trevor Noah on a social distancing episode of the "The Daily Show" on Thursday, calling in with a video chat. He called the novel coronavirus the "worst nightmare" when it comes to pandemics.

Fauci didn't mention Trump directly in the conversation, but he did dismiss ideas of opening the country in the coming weeks, like Trump's overly optimistic intent to bring things back to normal by April 12.

"The virus is the clock, Trevor," Fauci said. "So people say arbitrarily, 'Two weeks we're going to be OK.' It depends on the kinetics of the outbreak."

He said that because it remains unknown exactly how long it will take for the virus to slow down, a re-opening day is "unpredictable."

Trump told Fox News Tuesday that he wants to relax restrictions by April 12 so he can see "packed churches" for Easter.

Deaths from the coronavirus in the US surpassed 1,000 on Thursday, and domestic cases of COVID-19 surpassed 82,000.

Fauci told Noah that young people should be more concerned about the virus than they appear to be.

While older people and people with underlying respiratory condiments may have a higher risk when it comes to COVID-19, Fauci said people with no underlying conditions can still end up in the hospital.

"Even though you are young, you are not absolutely invulnerable," he said. "If you think you are completely invulnerable, you are incorrect."