There are two ways to launch a biological assault on the human race. The first is to evolve a lethal bacterium or virus against which we have no defence. The Aids, Ebola and Hanta viruses are examples.
Less feared, but just as deadly, are organisms which have found a way around our defences by evolving protection against the antibiotic drugs we use to destroy them. It is their indestructibility, rather than toxicity, which makes them lethal.
Forty years ago the Swan report warned that the practice of adding antibiotics to animal feed as growth promoters was endangering human health.
The reckless use of the drugs was fuelling the growth of resistant organisms against which we would have no defence. Antibiotic growth promoters were phased out in the UK from the mid-1990s and the practice was finally ended by an EU-wide ban in 2006.
Now the use of modern, more powerful antibiotics is growing again because the conditions in which animals are reared, crammed together in sheds, favour the spread of infection.
Four decades ago there was less worry about antibiotic resistance because new drugs were coming along to tackle resistant bacteria. But the supply of novel drugs for humans has dwindled to a trickle.
Discovering new agents has proved increasingly difficult and costly; they are only taken for a short period and the returns are low. Drug companies have had no incentive to search for them.
Overuse of antibiotics over the past 60 years, in human and animal medicine, has created this microbiological threat. It is time to revisit the Swan report.