Two MV Hondius passengers who died from hantavirus likely contracted the deadline infection while bird-watching in Argentina, investigators believe – then brought it on board the now-stranded cruise ship.

Argentine officials say a Dutch couple that succumbed to the virus last month picked it up from rodents while visiting a landfill during a bird-watching tour in the city of Ushuaia in mid-March, they told the Associated Press Wednesday.

However, there’s one big hole in the theory. Authorities previously said that the area and the surrounding province of Tierra del Fuego had never recorded a case of the hantavirus.

The passengers then boarded the MV Hondius, which departed on its 35-day-long expedition trip from the Argentine port on March 20.

Hantavirus is usually transmitted by inhaling the virus from infected feces or urine from mice or rats.

The 70-year-old Dutchman reportedly began feeling sick on April 6, with a fever, headache, abdominal pain and diarrhea. (Read more from “Health Officials Think They’ve Tracked Down Source of Cruise Ship Hantavirus Outbreak” HERE)