MADRID (AP) — More than two dozen passengers from at least 12 different countries left a cruise ship hit by a deadly hantavirus outbreak without contact tracing nearly two weeks after the first passenger died on board, the ship operator and Dutch officials said Thursday.

Health authorities on at least four continents are now tracking down and in some cases monitoring the cruise passengers who returned home on April 24, and trying to trace others who may have come into contact with them.

Experts say the risk to the wider public is considered low because hantavirus — usually spread by the inhalation of contaminated rodent droppings — isn't easily transmitted between people.