Dr. Anthony Fauci, head of NIAID. Photo: Drew Angerer/Getty Images

In testimony to Congress Wednesday, the government’s top infectious disease expert told lawmakers that the coronavirus outbreak in the U.S. is “going to get worse.”

“I can say we will see more cases and things will get worse than they are right now,” Dr. Anthony Fauci, director of the National Institute of Allergy and Infectious Diseases, told the House Oversight Committee. “How much worse it will get will depend on our ability to do two things: to contain the influx of people who are infected coming from the outside, and the ability to contain and mitigate within our own country,”

.@RepMaloney: "Is the worst yet to come?"



Dr. Anthony Fauci: "Yes, it is…We will see more cases and things will get worse than they are right now…Bottom line: it's going to get worse."



Watch full #Coronavirus hearing here: https://t.co/qUfpOTAqTq pic.twitter.com/RNBNiPrFN1 — CSPAN (@cspan) March 11, 2020

Fauci’s comments stand in contrast to President Trump’s attempts to dismiss the seriousness of the coronavirus outbreak that has so far infected 1,026 Americans and left 31 dead.

“It will go away. Just stay calm. It will go away,” Trump told reporters Tuesday. “Be calm. It’s really going to work out. A lot of good things are going to happen.”

On Monday, he compared the coronavirus outbreak to the common flu in a tweet.

So last year 37,000 Americans died from the common Flu. It averages between 27,000 and 70,000 per year. Nothing is shut down, life & the economy go on. At this moment there are 546 confirmed cases of CoronaVirus, with 22 deaths. Think about that! — Donald J. Trump (@realDonaldTrump) March 9, 2020

Fauci said the comparison is flawed. “I mean, people always say, well, the flu, you know, the flu does this, the flu does that. The flu has a mortality of 0.1 percent. This is ten times that. That’s the reason I want to emphasize we have to stay ahead of the game,” he said.

The seriousness of the coronavirus outbreak was underscored again Wednesday when the World Health Organization officially declared it a pandemic.

“This is the first pandemic caused by coronavirus,” WHO Director-General Tedros Adhanom Ghebreyesus said Wednesday. At the time of his announcement, there were approximately 124,000 cases of COVID-19, the illness caused by this particular coronavirus, in the world. More than 4,500 have died, most of them in China.

But the virus keeps spreading. “In the past two weeks, the number of cases of COVID-19 outside China has increased thirteenfold, and the number of affected countries has tripled,” Ghebreyesus said.

As for how many Americans will be affected, Fauci told lawmakers that depending on the public-health response, the number could be astronomical. “If we are complacent and don’t do really aggressive containment and mitigation,” he said, “the number could go way up and be involved in many, many millions.”