Medics have identified another passenger who came into contact with the man who contracted Crimean Congo Viral Haemorrhagic Fever.
The person will be monitored by doctors on a daily basis to track any developments of symptoms. However, health authorities have insisted these actions are merely precautionary.
Four passengers have now been determined to have come into close proximity to the 38-year-old man who returned to Glasgow from Kabul on Tuesday. Two have been determined not to require follow-up surveillance while another, who remained near the man during the flight, will be monitored for two weeks, the maximum incubation period for the disease.
This means that two passengers are currently being monitored for the deadly virus, in addition to the original patient.
Meanwhile, the 38-year-old has been taken by helicopter the Brownlee Unit in Glasgow to the Royal Free London NHS Foundation Trust.
Health chiefs said the move was in line with standard protocol for the management of severe and rare diseases.
He flew from Kabul in Afghanistan to Dubai, before getting a connecting Emirates flight EK027, which arrived in Glasgow at 12.35 pm on Tuesday.
His condition was stabilised at the Brownlee Unit before a joint operation of the Scottish Ambulance Service and the RAF transferred him to London. He continues to be listed as critical.
The risk to all other passengers on the flight is extremely low. The medical technicians who handled the patient's blood at the Brownlee Unit will be kept under observation for 14 days.
Dr Syed Ahmed, NHS Greater Glasgow and Clyde Consultant in Public Health who is coordinating the investigations into this case, said: "The risk of person to person transmission of Crimean Congo Viral Haemorrhagic Fever is extremely low as it can only be transmitted by direct contact with infected blood or body fluids.
"It is not a virus which is transmitted through the air. As such the risk to those who were in close contact with him is minimal. We have already made contact with all the patient's close contacts and they are being followed-up appropriately.
"The decision to transfer the patient to the high security unit at the Royal Free was taken in line with the national protocol for the management of cases such as this.”
The Royal Free Hospital houses the national specialist centre for the management of patients with hazardous infections.
The man is being treated in the high-security infectious diseases unit, which is maintained and run by specialists and is located in a purpose-designed area sealed and separated from other public and ward areas. It is a self-contained unit with its own filtered air supply and outlets.
Dr Ahmed said the fever is a "widespread tick-borne viral disease" which is not common in western Europe, but is "endemic" in parts of eastern and southern Europe, central Asia, Africa, the Middle East and the Indian subcontinent. It is fatal in around 30% of cases.
Sufferers initially show flu-like symptoms before developing haemorrhaging, changes in mood and sensory perception, and vomiting. Red eyes, a flushed face, a red throat, and petechiae (red spots) on the palate are common.
More severe symptoms include jaundice, acute kidney failure and respiratory problems.
Passengers who travelled on flight EK027 can call NHS24 on 08000 858531 for advice, information and reassurance.