The world is ill prepared for the looming threat of a biological terror attack, the head of Interpol has said.
Agencies are better prepared - but more must be done, Mr Noble said
Ronald Noble told the BBC the danger of an al-Qaeda attack had not diminished since the 9/11 strikes on the US.
The head of the global police body also denied governments had played up the risks for political gain.
"I don't think it is the sounding of false alarms," Mr Noble said, citing recent evidence. "I think the alarm is real and it is continuing to ring."
'Millions at risk'
Recent attacks around the world; indications that al-Qaeda plans to use biological and chemical weapons; and its statements claiming "the right to kill up to 4 million people" are "enough evidence for me to be concerned", Mr Noble said.
In an exclusive interview with the BBC's Ten O'Clock News, he warned that the potential cost of a biological terror attack left no room for complacency.
"When you talk about bio-terrorism, that's one crime we can't try to solve after it happens because the harm will be too great."
"How could we ever forgive ourselves if millions or hundreds... or tens of thousands of people were killed simply because our priorities did not include bio-terrorism?"
Around 400 police officers and health officials from around the world are going to the French city of Lyons next month to attend a bio-terrorism conference - the biggest ever organised by Interpol.
Mr Noble acknowledged that governments and security agencies were better organised against the threat than ever before - but "none of us can let our guards down and assume that the problem has been addressed".
Were al-Qaeda to launch a "spectacular biological attack which could cause contagious disease to be spread, no entity in the world is prepared for it", he said. "Not the US, not Europe, not Asia, not Africa."
Interpol's bio-terrorism conference, due to start on 1 March, will seek to encourage intelligence agencies and police forces to share information and co-operate more closely against the biological terrorism threat.