TL;DR
The WHO reports potential human-to-human transmission of hantavirus on a Dutch cruise ship where three passengers died. The virus is typically rodent-borne, but close contact among passengers raises concerns.
The World Health Organization has said it believes there may have been human-to-human transmission of hantavirus on the Dutch cruise ship where three passengers have died.
The virus is usually spread from rodents, but the WHO said in this instance it could have been spread among "really close contacts" onboard the MV Hondius vessel, before stressing that such transmission was rare and the risk to the public was low.
"Some people on the ship were couples, they were sharing rooms, so that's quite intimate contact," WHO official Dr Maria Van Kerkhove said.
The WHO suspects that the first person to fall ill could have contracted the virus before boarding the ship, Van Kerkhove said.
Two of the passengers who died were a Dutch married. The wife is confirmed to have had the virus.
One other passenger, a 69-year-old UK national who was evacuated to South Africa for medical treatment, is also confirmed to have the virus.
Hantavirus has not been confirmed in the Dutch woman's husband or the other deceased passenger - a German national who passed away on 2 May.
Testing is taking place for other passengers and crew members who are displaying symptoms.
The MV Hondius ship set sail from Argentina to start its voyage across the Atlantic Ocean around a month ago. It is currently anchored near Cape Verde, off the west coast of Africa.
Investigators are working under the assumption that the Andes strain of the virus, which spreads in South America where the cruise began, has been found in the two confirmed cases.
The organisation was told there were no rats on board, Van Kerkhove said, adding that the risk to the wider public from the disease was low and that hantavirus transmission between humans was uncommon.
She said disinfection was taking place on the ship and those with symptoms or caring for patients were wearing full personal protective equipment.
"Our working hypothesis is that there's probably a couple of different types of transmission that might be happening," Van Kerkhove told BBC Breakfast on Tuesday.
She noted the cruise had visited many different islands, some of which have rodents, which typically spread the virus through their faeces, saliva or urine.
The WHO's "top priority" remains treating the two crew members - of Dutch and British nationality - who were on board with respiratory symptoms, Van Kerkhove said.
They are due to be medically evacuated by aircraft to the Netherlands, alongside a person "associated" with the German national who died, according to the cruise ship's operator, Oceanwide Expeditions.
No-one else on the vessel has shown symptoms, the WHO says.
Some 149 people from 23 countries remain on the ship under "strict precautionary measures", Oceanwide Expeditions has said.
The ship was due to dock in Cape Verde on Tuesday, but local authorities have barred passengers from disembarking on safety grounds.