Every day Landon Spradlin was growing weaker, and now, on the morning when he would leave New Orleans for the last time, the 66-year-old preacher and blues guitarist was unable to load his bags into the white Ford F-250 that was supposed to carry him home. Ric Lyons, a fellow musician who for weeks had played and prayed with Spradlin amid the Mardi Gras crowds thronging Jackson Square, packed the truck. Spradlin’s wife, Jean, settled in the driver’s seat. Spradlin eased into the cab beside her. Racked by fits of coughing, the ordinarily talkative street minister said little as the Ford rolled east on the Twin Span Bridge across the wide, bright expanse of Lake Pontchartrain. The world had changed since the Spradlins crossed the same bridge weeks earlier to begin their annual New Orleans street ministry. The couple from rural Gretna, Va., had arrived Feb. 18, several days before President Trump declared on Twitter that the novel coronavirus was “very much under control in the USA.” They left on March 16, the same day the president would recommend that Americans stop gathering in groups of more than 10. New cases of covid-19, the deadly disease once confined to central China, were emerging rapidly across the United States. Cities and states were beginning to lock down. After a teeming Mardi Gras, New Orleans had canceled its similarly boisterous St. Patrick’s Day celebration. The French Quarter was all but empty. And the Spradlins were sick. This happened to them almost every year: After the crowds and the music, the conversations and prayers with countless strangers, they would come home from Louisiana with some kind of bug. Landon had bad lungs, and when he began wheezing in the days after Mardi Gras he assumed it was one of the periodic visitations of bronchitis, pneumonia or severe asthma he endured. Jean, who is 63, came down with a slight fever and shortness of breath.