Ever since we left our hunter-gatherer roots and began to domesticate crops and animals, we have made a pact with our food supplies that carries a cost. Animals provide us with an amazingly rich source of protein, but working closely with animals, and using their milk and meat and pelts, means that we are open to attack from their viruses too. Avian flu, swine flu, AIDS – just the tip of a mass of diseases that we have bought into with our insistence on being master of beasts.

Those who couldn’t survive this close contact soon died out, and initially those in the Middle East evolved tolerance to most animal diseases. When we eventually pushed out into the new world, it was germs, not guns, that killed most of the Inca.

It brings a new dimension to this metaphor of ‘the Lamb of God.’ With that slaughter and blood, comes infection. We are changed forever. There is no return.