In the blockbuster Contagion, Gwyneth Paltrow travels to Hong Kong on business and returns to suburban Minneapolis with flu-like symptoms. Within days she is dead. Paltrow is the index case in a pandemic that sweeps across the world. Contagion is a dramatic example of how a series of mundane, every day activities—such as shaking hands, drinking from a glass and blowing on dice for good luck—can rapidly and effectively spread disease.

Starting Friday, this year’s summer Olympics will kick off in London, the international hub of Europe. Can you imagine the potential for disease spread in a city that will host ten million athletes and tourists from all over the world? …