Hugh Pennington, emeritus professor of bacteriology at Aberdeen University, said there is "no way" of stopping people coming into the country who may be incubating the disease, as it can take weeks for symptoms to develop.
GPs and hospital doctors across Scotland have been placed on alert to identify any suspected cases of the disease, as the world's deadliest outbreak in West Africa shows no signs of abating.
More than 700 people have died since February - more than double the previous highest death toll of 280, which occurred during the first outbreak of the disease, in the Democratic Republic of Congo in 1976.
Last week, trade union leaders raised concerns that border, immigration and customs staff in the UK felt unprepared to try to deal with any potential cases of the virus in arriving passengers.
Pennington said yesterday: "There is no way we can stop people coming into the country who are incubating the disease, because if they are incubating the disease, they are not sick.
"That can go on for up to a couple of weeks after being exposed. Clearly if someone has been in a village where there has been a lot of ebola you wouldn't expect them to be coming here without telling someone.
"But it is just not possible [to screen all passengers] and it wouldn't work anyway - when they are incubating the disease they are not ill, so what you would be looking for?"
Ebola is one of a group of illnesses known as viral haemorrhagic fevers, which also includes Lassa fever and Marburg virus disease.
The main routes of infection are direct contact through blood and other bodily fluids, through broken skin or mucous membranes, or contact with splashes of blood or body fluids, with no evidence it can be spread through the air.
There is no cure for ebola, which has a fatality rate of up to 90%. Initial symptoms such as vomiting, diarrhoea, a rash and stomach pains can suddenly appear up to 21 days after exposure to the virus. In the later stages of the illness, the infected person may bleed internally and from the ears, eyes and mouth.
Pennington said a case of ebola emerging in Scotland was a "real possibility", but added it was unlikely as many of the countries worst affected by the outbreak were relatively poor and would not have huge numbers of travellers coming to the UK.
However, he said the first recorded case of ebola in Nigeria last week was likely to have triggered the flurry of activity in the UK, which included a meeting of the UK Government's emergency Cobra committee. The man, from Liberia, died after arriving at Lagos airport on Tuesday.
"We have a lot of people going backwards between Scotland and Nigeria, and England and Nigeria," Pennington said. "Nigeria is different from Liberia or Sierra Leone in the sense of travel.
"Having said that, we can be reasonably confident the Nigerians would not have any more cases spreading from that particular one.
"Time will tell and in a couple of weeks we will know. However, it does still raise the issue that here was a guy who was sick and went on an aeroplane."
Pennington said the "nightmare scenario" would be someone coming into a hospital in Scotland and not being diagnosed in sufficient time to prevent the virus spreading to staff.
Officials at Health Protection Scotland (HPS) also said that it is unlikely an early case would be picked up in a passenger arriving at an airport.
Dr Kitty Smith, medical lead for the travel medicine and international health team at HPS, said if an individual was unwell enough to be showing symptoms, they would be unlikely to be allowed to board a plane. She said: "It would be likely they would turn up at an A&E and the doctors would suspect a possible case based on their history.
"There is a very high level of awareness [among medical staff], because over the last few years guidance has been updated and is circulated to the relevant doctors.
"Recently, HPS has alerted GPs and all doctors, both primary and secondary care, to raise awareness to indicate what the guidance is."
Smith emphasised that no cases of ebola had been detected in Scotland.
"We have been testing for viral haemorrhagic diseases including ebola frequently over the last five years - not in huge numbers - but it isn't something we are only doing now," she said.
"If a clinician finds a patient has come from a relevant area and may have been exposed, that patient will be tested. To date they have all been negative."
The guidance, which is based on UK-wide guidelines for viral haemorrhagic disease, covers everything from flowcharts to help medics make a diagnosis to where patients should be treated, and what kind of protective clothing staff should wear when dealing with them.
Any patients in Scotland who become severely unwell with ebola will be taken to London's Royal Free Hospital, which has the UK's leading experts in dealing with viral haemorrhagic fevers - and a high-security infectious diseases unit.
Smith pointed out Glasgow had experienced dealing with a case of viral haemorrhagic fever in 2012, when a man arriving on a flight from Dubai was diagnosed with Crimean-Congo viral haemorrhagic fever, a disease similar to ebola. He later died, but the disease was not transmitted to anyone else.
"Ebola is very serious if you catch it, but it isn't that easy to catch," Smith said. "If somebody had it but was generally well, say in the early stages, they could be sitting next to you on the bus and it would not be transmissible to you."
A spokeswoman for the Scottish Government said there were no current plans for the Scottish Government's resilience committee - the equivalent of Cobra - to meet over the issue of ebola.
She said: "There are no cases of ebola in Scotland and it currently poses a very low risk to Scotland."