Problem with biological weapons is blowback, the user might end
up suffering from its effects as well. Hence while highly
terrifying and destructive, their actual strategic use
within rational belligerents is thankfully more
limited.
In some ways they may be more destructive then nuclear weapons.
You can deal with a nuclear attack if you know how to, a biological
threat is self-replicating and is far more chaotic in its spread.
Most rational military planners know this, hence while they have
stocks of biological weapons, the use of them is limited, if
ever.
All bets are off however, if you are talking about biological
weapons in the hands of a madman dictator with no grasp of
reality.
