To the degree that you think about influenza, it is probably because it is a bad flu season now, and you are either feeling smug that you got the shot, or wondering whether you should have. But there is a larger context for flu that affects the food world—and right now, flu is creating significant disruptions in international trade in food.

China has placed a hold on any imports of poultry or eggs from the US, a trade channel worth more than $270 million per year, because a particular strain of flu has been found in backyard poultry and wild birds in several Pacific Northwest states and in Canada. China is a large poultry-export market for the US, but in