Border, immigration and customs staff feel unprepared to deal with people coming to the UK with possible cases of the Ebola virus, a union leader says.
Immigration Service Union (ISU) general secretary Lucy Moreton said her members needed more information on the threat.
But the Border Force has insisted staff have been given guidance on how to identify and deal with suspected cases.
Almost 700 people have died in West Africa since the first case of Ebola was detected in February.
Foreign Secretary Philip Hammond said the government was taking the current outbreak - the world's deadliest to date - and the threat to the UK "very seriously".
Ebola is a viral illness - initial symptoms can include a sudden fever, intense weakness, muscle pain and a sore throat - that can cause internal and external bleeding.
It kills up to 90% of those infected but patients have a better chance of survival if they receive early treatment.
Mrs Moreton told BBC News that ISU members were "very concerned" and needed more information.
"They serve on the front line; they are the first point of contact usually for people coming off an aircraft and the concern is what do they do if they're confronted with someone that doesn't appear well who appears at the border," she said.
"There is no health facility at the border, there is no containment facility, and until extremely recently there has been no guidance issued to staff at all as to what they should do," she said on BBC Radio 4's The World Tonight.
Health facilities on planes and at ports
Smitha Mundasad, health reporter
Most UK airports have measures in place for people who are unwell - starting before they board the plane. Passengers who have high fevers or other signs of infectious illness may be advised not to fly, though exact policies depend on the individual airline.
If passengers become seriously unwell while flying, advice is sought from any health professionals who happen to be on board and ground control are alerted quickly.
Attempts may be made to isolate patients by clearing nearby seats. Where possible, sick passengers have a designated toilet for sole use and all contaminated surfaces are disinfected.
On arrival, anyone sitting within two rows of the patient are asked to leave their contact details in case needed.
Major airports may have medical experts nearby to examine people with any concerning symptoms. And officials often have agreements in place with local hospitals, allowing for quick transfer and treatment.
Some airports also have isolation facilities for people who need them.
A Border Force spokesperson said its priority remained the security of the border, which included helping to protect public health.
"We have well-established procedures for dealing with infectious diseases," the spokesperson said.
"We are currently working closely with partners such as Public Health England to minimise any potential risk and Border Force officers have already been given guidance on how to identify and safely deal with suspected cases of Ebola."
It is understood staff have been advised that if they identify someone as potentially infected, they must refer them to a specialist medical care provider - by ambulance if necessary.
The guidance also includes instructions to report the case to Public Health England.
Mr Hammond said the UK's health services had the experience to deal with the threat posed by the deadly virus.
He said the threat to Britain came from someone contracting the disease abroad and becoming unwell back in the UK, but the disease had not yet "directly" affected the UK.
Elsewhere, Dr Nick Beeching, senior lecturer at the Liverpool School of Tropical Medicine, told the BBC people were not going to catch the virus simply by being on a plane with an infected person.
"This is acquired by close contact with body fluids of people that are infected," he said.
"It's not spread through the air, like let's say flu or SARS, so it's a very different kind of transmission from those infections."
Several West African airlines have stopped flying to Liberia and Sierra Leone amid concerns about the spread of the disease to those countries from Guinea.
Authorities in Ethiopia and Kenya are to screen all passengers arriving from West Africa.
Meanwhile, the International Air Transport Association (IATA) said on Thursday that it was not recommending any travel restrictions or border closures after consulting the World Health Organization, according to Reuters.
Any risks would be low in the rare event of an Ebola sufferer travelling by air, it added.
It comes after an infected American man of Liberian descent was found to have flown from Liberia to Nigeria last week. He developed symptoms during the flight.
Schools have been shut and communities quarantined in Liberia in a bid to stem the outbreak. A public health emergency has been declared in Sierra Leone.
Earlier this month Public Health England issued an alert to UK doctors to be aware of Ebola symptoms.
Ebola virus disease (EVD)
- Symptoms include high fever, bleeding and central nervous system damage
- Fatality rate can reach 90%
- Incubation period is two to 21 days
- There is no vaccine or cure
- Supportive care such as rehydrating patients who have diarrhoea and vomiting can help recovery
- Fruit bats are considered to be virus' natural host