Passengers from the cruise ship struck by a hantavirus outbreak are being evacuated and sent to their home countries to isolate and receive medical treatment if necessary.

Some other passengers from MV Hondius left on earlier flights or connections and their contacts are now being traced as a precuation.

Officials say the risk of the infection spreading to the general public remains low.

Crew and passengers now face having to self-isolate for more than a month to avoid any potential spread.

Three died either on board or after travelling on the ship, which set sail from Argentina a month ago. Four others were medically evacuated from the ship for treatment.

So how worried should we be?

In an update on Thursday, Dr Maria Van Kerkhove from the World Health Organization (WHO) stressed it was not the start of a pandemic, saying: "This is not Covid, this is not influenza, it spreads very, very differently."

Unlike diseases such as measles, which are highly contagious and spread easily, the Andes strain of hantavirus behind the outbreak is not that infectious.

Human-to-human spread is possible but the risk of infections globally remains low, says WHO.

In a latest update, it says nine cases - seven confirmed by tests - have been identified in people who were on the ship.

It is still not clear how the outbreak started.

Hantavirus typically spreads from rodents, with people infected by breathing in air contaminated with virus particles from rodent urine, droppings, or saliva.

The cruise had been visiting remote wildlife areas, so a passenger could have come into contact with the virus then, or before boarding the ship.

Experts have observed the Andes strain spreading between human patients in previous outbreaks, through very close contact, and health experts believe that some of the infections on board MV Hondius may have passed between people.

Even luxury cruise ships have relatively cramped or restricted living conditions, with people sharing cabins and dining areas - places where infections could spread.

People can catch it from someone that they spend prolonged time with in close physical proximity.

The three deaths include a Dutch woman who left the MV Hondius when it stopped at the island of St Helena on 24 April. She had been sharing a cabin with her husband who previously died on board on 11 April - although it is not currently known if he is one of the confirmed cases of hantavirus.

Hantavirus is not spread in the outside world through everyday social contact like walking in public spaces, shops, workplaces, or schools, the UK Health Security Agency (UKHSA) says.

Symptoms usually appear between two to four weeks after being exposed to the virus, but can occur more than a month later, which is why the recommended isolation period for the passengers is so long.

People or "contacts" who may have been exposed to the infection - including on the boat, in hospital or on any of the flights that passengers took - will be monitored.

Contact-tracing work that is under way has been "quite a mammoth effort", Prof Robin May, chief scientific officer at the UKHSA has told the BBC, and one "we will continue to do... for some time".

Passengers returning from the cruise ship will be asked to self-isolate as a precaution.

Fourteen Spanish nationals face mandatory quarantine at a military hospital in the Spanish capital.

Twenty Britons are isolating at Arrowe Park Hospital in Merseyside, after their chartered flight from Tenerife landed at Manchester Airport on Sunday. They will stay there for 72 hours, before being asked to self-isolate for a further 42 days at home.

Prof May said all of the British evacuees were "healthy and asymptomatic".

Speaking to BBC Breakfast on Monday morning, he said "we may need to update" the period of isolation "depending on what the science tells us".

He reiterated that the risk to those not directly linked to the cruise is "extremely low indeed".

Meanwhile, one French passenger has shown symptoms of the disease while being repatriated to France.

An American passenger travelling to the US has begun showing mild symptoms of hantavirus and another has tested mildly positive for the Andes strain of the virus.

Both passengers were "travelling in the plane's biocontainment units out of an abundance of caution," the US Department of Health and Human Services said.

People ill with the Andes strain can have symptoms similar to flu - a fever, fatigue, muscle aches. They may also get shortness of breath, stomach pain, nausea and vomiting or diarrhoea.

Tests exist to diagnose the infection but there is no specific treatment, although early medical support in hospital can improve survival. Treatment is for the symptoms displayed.

After being flown to a medical centre in Nebraska, some Americans will be allowed to "self-isolate" in their home states.

The passengers landed in the UK on Sunday and none have reported symptoms, but they will will be monitored in hospital for 72 hours.

The American national has arrived in Nebraska, while a French woman is isolating in Paris.

The Merseyside site was last used to isolate those arriving from China at the start of the Covid pandemic.

The BBC reports from the city of Ushuaia, where experts have been sent to investigate the origins of the outbreak.