Throngs of passengers crowded major US airports Saturday evening after the onset of President Donald Trump's travel restrictions on people arriving from Europe amid a coronavirus pandemic.

Travelers and media outlets shared photos and videos of packed terminals at O'Hare airport in Chicago, Washington-Dulles in Virginia, and Dallas/Fort Worth airport in Texas.

Public health experts were astonished at the scenes, noting that the dense crowds presented the perfect opportunity for coronavirus transmission.

Local officials appeared furious, with Illinois' governor tweeting that "the federal government needs to get its s@#t together. NOW."

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Massive lines of travelers crowded into US airports Saturday evening, not long after President Donald Trump issued coronavirus-related travel restrictions on passengers arriving from Europe.

News outlets and passengers shared photos and videos of packed airport terminals at O'Hare airport in Chicago, Washington-Dulles in Virginia, and Dallas/Fort Worth airport in Texas as travelers awaited customs screening.

Public health experts bemoaned the scenes, noting that the dense crowds presented a perfect opportunity for coronavirus transmission.

"Good God. You could hardly invent a better scenario for superspreading events," tweeted Jeremy Konyndyk, a senior policy fellow at the Center for Global Development. "Any cases of COVID in these crowds will have a far higher chance of spreading to others in these lines than if they were just allowed in unchecked."

Another expert, biology professor Carl Bergstrom of the University of Washington, tweeted that the crowds were "a perfect storm for creating massive case clusters."

He continued: "To be clear, this is an absolute failing of policy and planning. This could have been entirely avoided. And now it will *without doubt* accelerate the epidemic of #COVID19 #coronavirus with the US."

—Katy Loves Soil (@katyslittlefarm) March 14, 2020

The travel restrictions come amid a growing coronavirus crisis across the world and within the US. In response to the pandemic, Trump suspended travel from many European countries for 30 days.

American travelers, legal permanent residents, and family members of both categories were exempt from the travel ban, but have had flights redirected and funneled into just 13 major US airports for enhanced screening.

At those airports — which include O'Hare, Dulles, and DFW — passengers were being asked about their medical history and current condition, and directed to self-quarantine for 14 days, according to the Department of Homeland Security.

DHS had warned on Friday that the new procedure might be "disruptive," but that the policies were meant to "protect the general public from further exposure and spread of the coronavirus."

One passenger told WGN News she waited up to four hours in the line-ups at O'Hare.

Illinois Gov. JB Pritzker appeared incensed on Saturday night, tweeting that the crowds were "unacceptable & need to be addressed immediately."

Prizker said the hold-up was due to the customs process, which is managed by the federal Customs and Border Protection agency.

"The federal government needs to get its s@#t together. NOW," Pritzker tweeted.

—Governor JB Pritzker (@GovPritzker) March 15, 2020

CBP told Insider in a statement Sunday morning that the situation had gotten better in several airports and that agents were working to process passengers safely and efficiently.

"We are aware of the reports of increased wait times at some airports across the nation. We understand this can be extremely frustrating, especially after a long flight. CBP along with medical personnel are working diligently to address the longer than usual delays," CBP's acting commissioner, Mark Morgan, said.

Morgan's statement continued: "We're continuing to balance our efficiencies with ensuring the health and safety of all American citizens through enhanced medical screening in accordance with CDC guidelines due to the global COVID-19 pandemic. Nothing is more important than the safety, health and security of our citizens."

O'Hare airport publicly acknowledged the situation, tweeting that staff was working with federal officials to prioritize screenings for elderly passengers and those traveling with young children.

The airport said it was also providing snacks and bottled water to those waiting in "longer-than-usual customs processing lines."

DFW Airport also noted there were "additional delays" while federal agents conducted "enhanced screening" for passengers.

The countries affected by Trump's travel ban included Austria, Belgium, Czech Republic, Denmark, Estonia, Finland, France, Germany, Greece, Hungary, Iceland, Ireland, Italy, Latvia, Liechtenstein, Lithuania, Luxembourg, Malta, Netherlands, Norway, Poland, Portugal, Slovakia, Slovenia, Spain, Sweden, Switzerland, and the United Kingdom.