The Urban H7N9 Virus

New communities add variance to the outcomes from social interaction. The probability of a big positive interaction goes up. So does the probability of a big negative one.Progress seems to come both from increases in this variance and from social systems that trim the lower tail. Together, they mean that we get the benefits of a big upper tail without the costs of the lower tail.In the history of physical communities, the most dangerous negative interactions came from infectious disease. It took centuries before clean water and rules about sanitation brought life expectancy in cities back up to rural levels.

Nearly all known bird-to-human flu jumps have occurred in rural settings, unfolding on and around farms. But not this H7N9: This may well be the first truly urban influenza in history. No infected rural flocks or farmers have been found in China. This outbreak started in one of the most modern, densely populated metropolises in the world: Shanghai.…Whatever animal harbors the virus, it must be an urban-adapted creature, and ubiquitous from China’s nearly tropical south to its wintry north. And because of the presence of those two crucuial “mammalian” mutations, it must have an internal ecology permissive to mammal-infectious forms of flu — which would seem to exclude birds, insects, amphibians — all but mammals.…Today, with the future path of the new influenza still uncertain, Beijing faces conundrums similar to those it confronted after publicly admitting to SARS. May Day, one of China’s biggest travel holidays, is approaching. Travel restrictions might be warranted to prevent nationwide spread if the virus is now thought to be geographically confined, and if further evidence shows that people can act as carriers and transmitters of H7N9. But the economic and geopolitical consequences of clamping down on social mobility are profound, particularly now that China’s economic growth is slowing.