The drama follows a fictional global epidemic
Smallpox 2002, to be broadcast on 5 February, is a fictionalised account of the spread of the killer virus.
It covers the first deaths in contemporary New York to an eventual global pandemic killing 60 million people.
The programme is backed by the BBC's current affairs department.
Some of the world's leading experts on bio-terrorism, such as Dr DA Henderson of the Centers for Disease Control, have been closely involved in the making of the drama.
'Frightening film'
Smallpox 2002 is being likened to such seminal BBC drama documentaries as Threads and The War Game, which in the 1970s and 1980s had a profound impact on people's awareness of the consequences of a nuclear attack.
"In its vivid and realistic portrayal of a devastating bio-terrorist assault, it raises serious questions - and should generate an urgent national debate - about our ability to defend against one of real threats to our security, post 11 September," he added.
The programme has been in development for two years, long before the recent anthrax deaths in the US.
But the drama has taken into account the recent anthrax outbreaks.
"The world started to catch up and we had continually to assess how real changes would affect our scenario," said Peter Horrocks, the BBC's head of current affairs.
"Things became more complicated but that made it seem more real."
The gap between reality and drama narrowed after 11 September when the US Government unveiled plans to stockpile enough doses of smallpox vaccine to protect every American citizen against the disease.
Technically eradicated in 1979, the smallpox virus can easily be passed from person to person, and the drama shows how one man passes the virus to scores of others while out walking.
The programme uses a strong documentary style to give the drama a believable edge said Mr Chinn.
News reports
"We have played a confidence trick on the audience," he said, adding: "It's a style that people are used to. We are hoping that people will engage with it as they engage with other documentaries."
The drama is set in 2005 and uses fictional interviews with those involved in controlling the outbreak, combined with news reports of the disaster.
A BBC Newsnight discussion on how the UK is prepared to face any real smallpox threat will be transmitted immediately after the drama, re-enforcing the fact the programme is rooted in fact and not fiction.
The programme will be backed up by a special site on BBCi, due to launch later this week.
Smallpox 2002: Silent Weapon is on BBC Two on 5 February at 2100GMT.