At Thursday’s news briefing, WHO’s Maria van Kerkhove said “this is not Covid, this is not influenza, it spreads very, very differently”.
She said authorities had asked “everyone to wear a mask” on board the MV Hondius.
Those in contact with or caring for suspected cases, she added, should “wear a higher level of personal protective equipment”.
At the same briefing, WHO Director General Tedros Ghebreyesus said his organisation “assesses the public health risk as low”.
He said the first two people with the confirmed virus had “travelled through Argentina, Chile and Uruguay on a bird-watching trip which included visits to sites where the species of rat known to carry the virus was present”.
Dr Tedros said the WHO was aware of reports of other people with symptoms who may have had contact with passengers, adding that officials were in touch with the relevant authorities.
Given the incubation period of this disease – which can be up to six weeks – it was possible more cases may be reported, he said.
Earlier on Thursday, Oceanwide Expedition said 29 passengers, of at least 12 different nationalities, had left the MV Hondius in St Helena, the British Overseas Territory. The Dutch government put a number of those who had disembarked the ship at 40, including a Swiss national who has now a confirmed virus case.
Seven were British nationals.
“Two of these individuals are now self-isolating in the UK while the others have not yet returned,” an update from the UK Health Security Agency (UKHSA) said. Four remained in St Helena – and “tracing efforts are ongoing for the seventh individual, who we know has not yet returned to the UK”, the statement said.
St Helena is one of the remotest islands on Earth, at 47sq miles (127 sq km)- a third of the size of the Isle of Wight – with a population of about 4,400 and one hospital.
The Dutch woman who had the virus and later died in South Africa was among those who left in St Helena.
Three other people – British, Dutch and German nationals – were evacuated from the vessel on Wednesday.
