CHICAGO — At 7 p.m. on Saturday night, my husband and I landed at O’Hare International Airport aboard a nonstop Turkish Airlines flight from Istanbul, returning home after 10 days in Qatar and Oman, where my husband had given a professional talk and we’d tacked on a vacation. We’d certainly been following the news about the progression of the covid-19 outbreak and President Trump’s knee-jerk travel ban. But because we hadn’t visited any Level 3-designated countries and were asymptomatic, we stuck to our originally scheduled plan to fly back Saturday.