I agree that hopefully the cruise lines have or will do some vetting with the ports. At the least they have some arrangement to offload the sick passengers for treatment if the port/country had the resources. Whether or not they can reach an agreement to also allow the passengers and crew to leave the ship in port would be a consideration and another problem. In thinking about the Caribbean there are islands out there saying they are open and want the business but some have virtually no medical capability for even their residents.