Dr Ewan Gerard, port medical director at Gatwick Airport, said that although it was an unlikely scenario, the potential was there for the virus to be used as a weapon.
And he said that as there had been no cases in the UK since 1978, few, if any, GPs would have seen it first hand.

It was vital every medic knew how to recognise smallpox and got themselves fully trained on how to deal with it and other rare diseases, he said.

"Smallpox in my opinion is not about to make a come back or be a major terrorist threat, but there is the potential.

"There are only two laboratories that are legally allowed to hold the smallpox virus and they are in Russia and in America."

But he said there were concerns that rogue states or individuals could be given the virus by the CIA and use it as a weapon.

The World Health Organization (WHO) has responded to concerns about bio-terrorism by agreeing to postpone the destruction of the world's last remaining stocks of smallpox virus, in preparation for mandatory immunisation.

But the deaths of five people from anthrax in the US following the 11 September attacks on New York and Washington heightened fears that the US government might resort to biological or chemical weapons, including smallpox, to consolidate power.