A man being treated for Crimean-Congo haemorrhagic fever after returning to the UK from Afghanistan has died, the hospital said.
It is the first laboratory-confirmed case of CCHF in the UK, according to the Health Protection Agency (HPA).
Other passengers who sat close to him on an aircraft are undergoing daily health checks.
"Crimean-Congo haemorrhagic fever can be acquired from an infected patient only through direct contact with their blood or body fluids, therefore there is no risk to the general public," the Royal Free London NHS Foundation Trust said.
"We would like to extend our condolences to his family."
The man, 38, was diagnosed when he returned to Glasgow on a flight from Kabul, Afghanistan, on Tuesday.
He had flown into Scotland on a connecting flight from Dubai.
The man, who has not been named, was being treated in isolation at Gartnavel General Hospital's Brownlee Centre, which specialises in infectious disease.
Yesterday he was flown from Scotland to a high-security infectious diseases unit at London's Royal Free Hospital.
The hospital houses the national specialist centre for the management of patients with hazardous infections.
Concerns have been raised for people who were sitting close to him on his plane journey.
NHS Greater Glasgow and Clyde said it has identified and contacted four passengers who may have had contact with the patient.
The health board said two of them - one who remained in "close proximity" to the ill man during the flight - will be monitored on a daily basis for the next two weeks for any developments of relative symptoms. The other two passengers do not require follow-up surveillance and the risk to all other passengers on the flight from Dubai is "extremely low", it added.
In a statement, the board said: "In total therefore we are currently following up two passengers from the flight with daily monitoring as a precaution for two weeks - two weeks is the maximum incubation period for the disease."
CCHF is especially common in east and west Africa.
It is fatal in about 30% of human cases.