IN America’s southwest, the indigenous Pima tribe have a frightening phrase, oimmeddam or wandering sickness—the sickness that crosses all borders.

The Pima story goes like this:

“Where do you come from? an Indian asks a tall, black-hatted stranger.

I come from far way, the stranger replies, from…across the Eastern Ocean.

What do you bring? the Indian asks.

I bring death, the stranger answers. My breath causes c