The cruise ship MV Hondius is anchored outside Cape Verde's capital Praia, but no one on board is allowed to leave the ship after a hantavirus alarm.
Three passengers have died and one is being treated in an intensive care unit in South Africa, where he is being isolated. In addition, two crew members have fallen ill, the only people still on board suspected of having contracted the virus.
Oceanwide Expeditions, which is arranging the cruise, now hopes that the ship will be allowed to dock in the Canary Islands and that further medical checks can be carried out there. Spanish authorities have not commented on the report.
No Swedes
So far, however, hantavirus has only been confirmed in one of the cases, according to the World Health Organization (WHO) - the British man being treated in South Africa. It has not been confirmed in the three deaths: a German man who died over the weekend and remains on board, and a Dutch couple in their 70s who died in April after leaving the ship on the island of St. Helena on April 11.
A total of 148 people are on board MV Hondius, of whom 87 are passengers.
According to Oceanwide Expeditions, they come from 23 different countries - none of them are Swedish citizens according to the passenger list. The Swedish Foreign Ministry also has no information about affected Swedes, the press service reports.
Do not panic
Very little information has come from the ship, which left Argentina in early April for Cape Verde, but an American passenger has taken to social media to urge caution against vilifying those on board and their families.
"All we want right now is to feel safe, get clarity on what is happening and just get home," he said, according to German Bild .
Hantavirus is often spread by rodents such as voles, but it can also be transmitted between humans. According to a statement from WHO European regional director Hans Kluge, there is a low risk to the public from the virus and there is no reason for panic or travel restrictions.
Hantavirus gained attention last year when the late actor Gene Hackman's wife, Betsy Arakawa, died after being infected with the virus.
Facts: Hantavirus
Hantavirus infections are caused by around 35 different closely related variants of hantavirus that have been reported worldwide.
Hantavirus infection is a zoonosis, that is, a disease that can be transmitted between animals and humans.
In Sweden, only the Puumala virus variant, which causes the disease bat fever, is found.
Depending on the type of hantavirus, people can suffer from anything from completely asymptomatic infections to very severe forms of hemorrhagic fever or acute pulmonary syndrome with a high mortality rate.
The virus particles come primarily from the rodents' urine and feces. When it dries, it can become airborne and infect people.
A common way to come into contact with the virus is in a summer cottage after the winter if you sweep up vole droppings instead of damp-wiping them. Then virus particles can be released into the air you breathe. It can also be found in wood where voles have lived.
According to the US Centers for Disease Control and Prevention (CDC), the mortality rate varies depending on the variant of hantavirus involved. For some severe forms of hemorrhagic fever or acute pulmonary syndrome, the mortality rate can be up to 35 percent.
