Writing in a New England Journal of Medicine perspective piece published on Wednesday, Anthony Fauci, director of the National Institute of Allergy and Infectious Diseases, and colleagues “look at the genetic sequences of past flu pandemics to learn how a virus goes from infecting only chickens or pigeons to sickening millions of people globally,” NPR’s “Shots” blog reports. Although the newly identified H7N9, which has infected 132 people and killed 37, “doesn’t transmit easily between people, some scientists have worried that it could gain that ability,” the blog writes. Though the virus has some mutations that help it infect human cells, and “[t]hese mutations are also found in flus that have caused pandemics, … Fauci and his colleagues say that’s not the way other flu pandemics came about,” according to “Shots.” Instead, in the three flu pandemics since 1957, the virus, related closely to the Spanish flu, “underwent large, sweeping genetic changes to create the contagion that swept across continents,” the blog writes, adding, “Fauci and his colleagues say these historical precedents are ‘only slightly reassuring’ for H7N9” (Doucleff, 6/6). In related news, two reports published on Thursday in the journal Cell describe how H7N9 and H5N1 flu strains could mutate to become better adapted for human-to-human transmission, HealthDay reports (Reinberg, 6/6).