The Fiji Ministry of Health and Medical Services is investigating the deaths of two United States citizens who arrived in Fiji on Wednesday 22 May.
The couple presented with an illness while holidaying in the Western Division.
They were provided with medical treatment but their illnesses progressively worsened and despite best efforts, they died within a few days of each other.
A US media report says the couple's family believe they might have contracted a virus.
The Fiji Sun gives the couple's names as 38 year old David James Paul and 35 year old Jane Michelle Canalog Paul.
They had been staying at Denarau Island and five people who came into contact with them have been placed under observation.
At this stage the Ministry is conducting investigations into the possible causes and has also put in place public health measures.
The Ministry is also working with the Fiji Police's forensics department, the World Health Organisation, and the United States Centres for Disease Control and Prevention, on determining the cause of death.