The World Health Organization (WHO) says it has told 12 countries that their citizens got off a cruise ship called the MV Hondius.
The ship is on a remote British island called Saint Helena.
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There is a deadly virus called hantavirus on the ship.
The WHO believes the outbreak will be small if countries follow public health rules and work together.
The 12 countries are:
Canada, Denmark, Germany, the Netherlands, New Zealand, Saint Kitts and Nevis, Singapore, Sweden, Switzerland, Turkey, the United Kingdom, and the United States.
So far, there are five confirmed cases of hantavirus and three more suspected cases. Three people have died.
The virus involved is called the Andes virus, which comes from Latin America.
No other passengers or crew on the ship have symptoms now. But the virus can take up to six weeks to show signs. So more cases may appear.
This virus usually spreads from infected rats through their urine, droppings, or saliva.
The Andes virus is special because it can also spread from person to person.
The WHO says this is not the start of an epidemic or a pandemic like COVID-19. This virus spreads very differently.
Two sick people are in hospital in the Netherlands. One patient in South Africa is getting better.
The ship is now sailing toward Tenerife, where passengers can go home.
The ship’s captain says morale on the ship has improved.