If anyone looks at a map, with states affected, it follows I-95 corridor on east coast, I-70 from California, Nevada, Utah, Colorado, Iowa, Illinois, Indiana, all the way to the East coast. Along the west coast, the virus follows the I-5, all the way to Seattle. North south, it is following the 35 from Texas to Minnesota.
Forget about airports, it is truck drivers who are vectors for spreading the disease in the United States.
Tracking Every Coronavirus Case in the U.S.: Full Map
Do truck drivers get a great deal on cruises? Because what I'm seeing is the west coast cases are related to travel at the onset, then local spread. Be it airflights from China or on Korea, or cruises. That seems to be the nidus event.