Should We Be Worried About Bird Flu?

The prevalence of the virus in our milk supply may also be less alarming than it sounds. The P.C.R. test used to identify it can detect minuscule amounts of genetic debris, and a positive result does not imply that the virus is alive, much less contagious. Nearly all milk sold in the U.S. is pasteurized—heated to destroy potential pathogens—and that process may be especially effective for unstable viruses such as influenza. (Many states—some, recently, as part of a broader backlash against public-health measures—have legalized the sale of raw milk, which health officials generally do not advise consuming.) The tests needed to conclusively determine whether pasteurization kills H5N1 take time and involve injecting eggs with milk samples, but, according to the F.D.A., preliminary studies haven’t found any traces of live virus.