Two men aged 65 and 67 had been on the ship and also the same flight as a confirmed hantavirus case from St Helena to Johannesburg on April 25, the CDA said.

Both arrived in Singapore in early May and have been isolated and are being monitored at Singapore’s National Centre for Infectious Diseases (NCID). The confirmed case did not travel to the city-state and died in South Africa.

“Two Singapore residents had been on board the cruise ship MV Hondius, which has reported an outbreak of Andes hantavirus. Both individuals have been isolated at the National Centre for Infectious Diseases, where they are being tested for hantavirus,” a CDA statement said.

“Their test results are pending. One has a runny nose but is otherwise well, and the other is asymptomatic. The risk to the general public in Singapore is currently low.”

If the pair test negative for hantavirus “they will be quarantined for 30 days from the date of last exposure”, CDA said, adding that “testing will be conducted again before release from quarantine”.

If they test positive they will remain hospitalised for monitoring and treatment, and “contact tracing will be conducted to identify persons who have been exposed during the infectious period, and close contacts will be quarantined”, the CDA said.

The MV Hondius has been at the centre of an international health scare since Saturday, when the UN’s health agency was informed that three passengers had died and the suspected cause was hantavirus.

Eight cases, including three deaths, had been linked to the cluster on the cruise ship by Wednesday, according to CDA.

The rare disease is usually spread from infected rodents, typically through urine, droppings and saliva.

However, experts have confirmed that the version of the virus detected aboard the Hondius is a rare strain that can be transmitted between humans.