Poland's foreign ministry spokesman Maciej Wiewiór confirmed on Tuesday there is one Polish national on board – a crew member – who does not require medical or consular assistance.
He added that hantavirus is a disease also found in Europe, including Poland.
Meanwhile, the WHO said it suspected some human-to-human transmission had taken place on board the Dutch-flagged MV Hondius, according to Reuters.
"We do believe that there may be some human to human transmission that's happening among the really close contacts – the husband and wife, people who have shared cabins," said Maria Van Kerkhove, the WHO's director of epidemic and pandemic preparedness.
Three people have died – a Dutch couple and a German national – while a British passenger is in intensive care in South Africa.
Seven confirmed or suspected cases have been reported in total.
The ship, carrying around 150 passengers, is currently off Cape Verde, which has not allowed it to dock.
The WHO believes the initial infections occurred before passengers boarded, after the Dutch couple had been travelling in Argentina.
Others may have been exposed during shore excursions to islands where birds and rodents are present.
There were no rats found on board, the WHO said.
The Hondius departed southern Argentina in late March on a luxury Antarctic expedition cruise.
The plan, according to Reuters, is for the ship to proceed to the Canary Islands, though Spain said it had yet to make a decision on receiving it.
Hantaviruses are typically spread through contact with infected rodents.
Human-to-human transmission is rare but has been observed in some previous outbreaks involving the Andes strain, which circulates in South America and which the WHO believes may be involved in this case.
(ał)
Source: Reuters, PAP