Bird flu is here to stay. The H5N1 avian influenza is proliferating among U.S. cows and there are now two strains circulating among mammals and birds. Though there are only 68 confirmed cases in people—largely dairy workers—public-health officials think bird flu is likely more widespread. Last week, a CDC report documented three asymptomatic cases in veterinarians who took care of cattle they didn't know had H5N1.
