How worried should we be about getting Hantavirus?

Watch: Hantavirus evacuees land in Amsterdam and are escorted to hospital

The outbreak of hantavirus on a cruise ship carrying passengers from across the world is a situation that authorities say they are taking incredibly seriously.

Three passengers have died either on board or after travelling on the ship, which set sail from Argentina a month ago.

Four others have been medically evacuated from the ship for treatment.

A huge operation is in place to trace people potentially exposed to the virus who have already taken flights home to numerous countries, including the UK, South Africa, the Netherlands, the US and Switzerland.

Health experts stress the risk to the general public is low. 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 its latest update, it says eight cases - five confirmed and three suspected - 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 UKHSA, external says.

Symptoms usually appear between two to four weeks after being exposed to the virus, but can occur more than a month later. 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 UK Health Security Agency (UKHSA) has told the BBC, and one "we will continue to do... for some time".

Any British passengers returning from the cruise ship will be asked to self-isolate in the UK for 45 days as a precaution, the UKHSA says.

For the broader public, not directly involved in this cruise ship, "the risk here is really negligible", Prof May adds.

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.

The UKHSA said officials were working to co-ordinate the arrival of British nationals to the UK from MV Hondius.

Dr Meera Chand, deputy director for epidemic and emerging infections at UKHSA, said: "It's important to reassure people that the risk to the general public remains very low.

"We are contact tracing anyone who may have been in contact with the ship or the hantavirus cases to limit the risk of onward transmission."

The MV Hondius is now sailing towards Spain's Canary Islands after being anchored for three days near Cape Verde, an archipelago nation off the West African coast.

The plan is for the remaining passengers and crew to fly to their home countries.

Local health authorities have visited the vessel and assessed the situation.