Chaos gripped major US airports Sunday as Americans returning from coronavirus-hit European countries overwhelmed authorities attempting to process the surge.Frustrated passengers complained of hours-long lines, crowded and unsanitary conditions and general disarray in the system for screening people for symptoms of the virus."Very close quarters," Ann Lewis Schmidt told CNN, describing conditions at Chicago's O'Hare International Airport. "So if we didn't have the virus before, we have a great chance of getting it now!" Schmidt said.US airports have been hit with a flood of Americans, many of them students, since restrictions on travel from Europe ordered by US President Donald Trump took effect at midnight Friday.The airport bottlenecks were the latest evidence of continuing turbulence in the administration's response to a pandemic that started in China in December and has since spread worldwide.READ | With store shelves emptying, Trump assures US has 'no shortages'On Sunday, the president reacted to news of the airport backups, saying on Twitter: "We are doing very precise Medical Screenings at our airports. Pardon the interruptions and delays, we are moving as quickly as possible, but it is very important that we be vigilant and careful."We must get it right. Safety first!"Turbulent responseThe United States on Saturday extended the ban on travel from Europe, South Korea and China to Britain and Ireland. Only US citizens and legal residents are being allowed in from those countries, and they are then supposed to self-quarantine for 14 days.READ | Billions wiped off South Africa market in minutes amid global bloodbathIn the United States, more than 60 people have died from the virus and more than 3,200 have been infected, according to a running tally kept by Johns Hopkins University.But the epidemic has outpaced the government's capacity to measure its true scope through wide-scale testing as some countries like South Korea have managed.Here are all the border post South Africa is closing to combat Covid-19 | @BISouthAfrica https://t.co/zlvYVDTr1K pic.twitter.com/mC46h3zHN5— News24 (@News24) March 16, 2020That has led to fears of an accelerating surge of cases, as Italy has experienced."I think Americans should be prepared that they are going to have to hunker down significantly more than we as a country are doing," Anthony Fauci, the country's leading expert on infectious diseases, told NBC's "Meet the Press.""I think we should really be overly aggressive and get criticized for over-reacting," said Fauci, director of the National Institute of Allergy and Infectious Diseases.READ | Coronavirus: Some varsities shut doors, others wait following Ramaphosa's addressSchools, museums, sports arenas and entertainment venues have closed in some states, but St Patrick's Day celebrations still filled bars and restaurants over the weekend, leading some local officials to consider more extensive shutdowns."We are certainly looking at that," said Governor Mike DeWine of Ohio, speaking on NBC's "Meet the Press."https://t.co/pdTxfqQbDI | Two Oceans Marathon cancelled amid coronavirus pandemic https://t.co/N3nhkmb45I— News24 (@News24) March 15, 2020Noting the lockdowns in Europe, Illinois Governor JB Pritzker said on the same show, "It's something that we're seriously looking at."Trump tests negativeTrump, who had played down the risks of infection early on, was himself tested for the virus Friday night, days after potentially being exposed to it during a visit by Brazil's President Jair Bolsonaro."This evening I received confirmation that the test is negative," the president's physician Sean Conley said in a Saturday memo.OPINION | Many of us will get the coronavirus and some will dieContrary to medical advice, the president was seen Friday shaking hands all around as he gathered his coronavirus response team at the White House. He attributed the practice to long-time habit as a politician but said he would have to change it.https://t.co/By0KBr5HQV | Kenya blocks entry for non-residents in virus response https://t.co/Foew4VYGIQ— News24 (@News24) March 15, 2020The White House had announced earlier in the day that "out of an abundance of caution, temperature checks are now being performed on any individuals who are in close contact with the president and vice president."Travel banTrump advised against non-essential travel, and said officials were considering imposing travel restrictions within the United States."If you don't have to travel, I wouldn't do it," Trump told the news conference. "We want this thing to end. We don't want a lot of people getting infected."ALSO READ | How Premier League stars keep busy during the coronavirus shutdownTrump spoke to British Prime Minister Boris Johnson on Saturday about the new restrictions, according to the White House press office.European officials have reacted angrily to Trump's sweeping travel ban, which also caused widespread consternation among travelers.The original 30-day US ban on travel from the 26 countries in Europe's Schengen border-free zone took effect on Saturday, but excluded Britain and Ireland. They were subsequently included.