A third British national is now suspected of contracting hantavirus in connection with the outbreak aboard the cruise ship MV Hondius, according to government officials.
The latest patient is currently on Tristan da Cunha, a remote island in the South Atlantic where the ship stopped in mid-April.
So far, two other British men have tested positive for the virus. One of them, 56-year-old expedition guide Martin Anstee, was evacuated to the Netherlands on Wednesday and is said to be in stable condition.
Another British passenger, aged 69, was flown to South Africa last month and remains in intensive care, although officials say his condition is improving.
Authorities have confirmed five hantavirus infections linked to the voyage, including one involving a passenger who later died.
The MV Hondius is expected to arrive in the Canary Islands this weekend.
British authorities say a chartered aircraft will be waiting to return UK passengers and crew home. Even though none of the remaining Britons onboard are showing symptoms, they are expected to self-isolate once they arrive in the UK.
Anstee, a retired police officer working as an expedition guide on the ship, was evacuated alongside a Dutch crew member and a German passenger.
Speaking briefly to the BBC, he said he was “fine.”
Health officials are also monitoring two other British nationals who already returned to the UK after possible exposure.
Both are self-isolating voluntarily and have not developed symptoms.
The group was among 30 passengers from several countries who left the ship on the island of St Helena on April 24, before the first confirmed hantavirus case was identified on May 4.
Four British passengers who disembarked on St Helena are still on the island and remain in contact with health authorities. Medical personnel are expected to be sent there as a precaution.
Officials say passengers connected to the outbreak may be asked to isolate for up to 45 days after returning home.
Meanwhile, international contact tracing efforts are ongoing in countries including Switzerland and the Netherlands as authorities try to reach passengers who left the ship before the outbreak became known.
The World Health Organization has described the situation as serious but stressed that the overall risk to the public remains low and is not comparable to the Covid-19 pandemic.
Investigators are still trying to determine the source of the outbreak.
WHO Director-General Tedros Ghebreyesus said the first infected passengers had recently travelled through Argentina, Chile and Uruguay on a bird-watching tour that included areas known to have rodents capable of carrying the virus.
One of the passengers who died was a 69-year-old Dutch woman who left the ship at St Helena before travelling to South Africa, where she later died. Her husband died earlier onboard the vessel, while a German woman also died during the voyage. Neither death has yet been officially linked to hantavirus.
Hantavirus is usually spread through contact with infected rodents, particularly rats and mice.
However, experts believe there may have been limited human-to-human transmission among passengers who were in close contact.
Symptoms can appear between two and four weeks after exposure and may include fever, severe fatigue, stomach pain, vomiting and breathing difficulties.
The UK Health Security Agency said the virus does not spread through casual everyday contact, adding that the rare cases of person-to-person transmission typically involve prolonged close interaction.
