Mark Zuckerberg livestreamed an interview with Dr. Anthony Fauci in which the nation’s leading expert on infectious diseases addressed urgent concerns of Americans as the coronavirus continues to spread.

Fauci, the director of the National Institute of Allergy and Infectious Diseases, spoke with the Facebook CEO live on Facebook on Thursday after "Where is Dr. Fauci?" trended on Twitter when Fauci did not appear at a White House news conference.

In his just-the-facts style, Fauci told viewers he expects social distancing and shelter-in- place measures to extend beyond 15 days. The U.S. is still in the "escalation phase" and how effective we are at fighting the virus will depend on how much we distance ourselves from one another, he said.

Fauci also emphasized that everyone should limit their exposure to others, including teenagers and young adults.

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His hope is that coronavirus will respond to social distancing like Severe Acute Respiratory Syndrome (SARS), a virus in the same family, but he warned that coronavirus transmits differently.

"What I certainly would like to see is what happened with SARS," Fauci said. "When public health measures essentially suppressed it, it disappeared and never came back."

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How the coronavirus is transmitted isn't precisely known yet. But we do know it spreads "too efficiently," Fauci said.

Asked by Zuckerberg for his projections in coming weeks, Fauci said: “We now are still in the escalation phase. How high that gets and how long it’s going to take to turn around is going to depend on how well we do containment and mitigation.”

The interview, which lasted nearly 40 minutes, came as Facebook attempts to put COVID-19 information from trusted health authorities in front of its billions of users to counteract the dangerous misinformation circulating on the platform that could lead to people engaging in risky behavior.

On Wednesday, Facebook announced it would put the latest news and updates about the pandemic at the top of the news feeds of its more than 2.5 billion users.

The new feature, the Coronavirus (COVID-19) Information Center, was built in collaboration with top health organizations such as the Centers for Disease Control and Prevention and the World Health Organization. It will include real-time updates from health authorities and organizations and will offer resources and tips on how to stay healthy and support your family and community.

As public fear and uncertainty grow with the rise in deaths and confirmed cases across the U.S., people are becoming increasingly susceptible to wildly false and sometimes hazardous claims that tap into our urgent need for the latest information about how to protect ourselves and our families.

So much misinformation is being transmitted from person to person that the scale is unprecedented, public health experts say. Unlike localized disasters such as hurricanes or mass shootings, the coronavirus outbreak is dominating the public conversation on every single social media platform.

Nearly half the public say they’ve been exposed to at least some fabricated news and information about the virus, according to a new Pew Research Center Election News Pathways survey. About a quarter said the coronavirus was deliberately developed in a lab and another 6% said it was accidentally made in a lab, both conspiracy theories circulating on social media.