The international sharing of virus data is critical for protecting populations against le-thal infectious disease outbreaks. Scientists must rapidly share information to assessthe nature of the threat and develop new medical countermeasures. Governmentsneed the data to trace the extent of the outbreak, initiate public health responses,and coordinate access to medicines and vaccines. Recent outbreaks suggest, however,that the sharing of such data cannot be taken for granted – making the timely inter-national exchange of virus data a vital global challenge. This article undertakes the?rst analysis of the Global Initiative on Sharing All In?uenza Data as an innovativepolicy effort to promote the international sharing of genetic and associated in?uenzavirus data. Based on more than 20 semi-structured interviews conducted with key in-formants in the international community, coupled with analysis of a wide range ofprimary and secondary sources, the article ?nds that the Global Initiative on SharingAll In?uenza Data contributes to global health in at least ?ve ways: (1) collating themost complete repository of high-quality in?uenza data in the world; (2) facilitatingthe rapid sharing of potentially pandemic virus information during recent outbreaks;(3) supporting the World Health Organization’s biannual seasonal ?u vaccine strainselection process; (4) developing informal mechanisms for con?ict resolution aroundthe sharing of virus data; and (5) building greater trust with several countries key toglobal pandemic preparedness.