Plates of sugar could indicate the deadliness of a flu strain. The influenza virus infects the body using hemagglutinin, a viral protein that latches onto sugars containing sialic acids on human cell surfaces. Scripps Research Institute investigators and their colleagues developed arrays containing 200 different carbohydrates and sugary proteins, representing the major types of molecules to which hemagglutinin might attach. They tested eight different flu strains, including the deadly 1918 influenza, and discovered that alterations at as few as two positions on the hemagglutinin protein can transform a bird strain into one that can infect humans. The scientists, who report the work in the February 3 Journal of Molecular Biology, say that the arrays could explain why the 1918 flu, which strongly resembles avian viruses, was so devastating. They could also lead to monitors that quickly determine how close another bird strain is to mutating into a pandemic form.