A video filmed by a passenger on board the MV Hondius shows its captain saying that a man who had died there passed away due to "natural causes".
The captain aboard the hantavirus-hit cruise ship can be seen telling passengers on 12 April that a doctor had said the individual was "not infectious".
Three confirmed and five suspected cases of hantavirus - a rare but severe disease usually spread by rodents - have since been identified.
Turkish YouTuber Ruhi Çenet, who was on board the cruise ship and filmed the announcement, told the BBC that no immediate safety precautions were taken at the time.
Around 150 people from 23 countries are currently stranded on the vessel near Cape Verde, off the west coast of Africa.
Oceanwide Expeditions, the cruise ship operator, told the BBC the first report of hantavirus came "after disembarkation at St Helena" and says it "acted as we reported via our press updates" following the first identified hantavirus case on 4 May.
