Botulism is a serious, potentially fatal illness caused by a type of poison. The poison – known as botulinum toxin – is produced by a kind of bacteria. Botulinum toxin is the strongest poison known to science. Botulism is always considered a medical emergency. It can cause death by paralyzing the muscles people use to breathe. However, over the past 50 years, with better care, the death rate for people with botulism has dropped from 50 percent to eight percent.